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At least 973 records · Page 54Linked to original sources
PubMed2005

p53 Codon 72 polymorphism predicts the pathologic response to neoadjuvant chemotherapy in patients with breast cancer.

PURPOSE: Recent studies have highlighted that the p53 codon 72 polymorphism plays a crucial role in modulating wild-type p53 apoptotic capacity, and as such may influence the response to chemotherapy. Thus, the purpose of this study was to investigate whether the p53 codon 72 polymorphism might influence pathologic response to neoadjuvant chemotherapy in primary breast cancer. EXPERIMENTAL DESIGN: One hundred and ten operable breast cancer patients received anthracycline-based neoadjuvant chemotherapy and p53 codon 72 polymorphism status was analyzed by PCR-RFLP. RESULTS: The distribution of initial clinical stage, tumor size, estrogen receptor or progesterone receptor status, menopausal status, or erbB2 expression was not significantly different among the polymorphic variants. However, we found that only 13% (3 of 23) of patients with the Pro/Pro variant had a good pathologic response, defined as a complete pathologic response or minimal residual disease. In comparison, 40% (22 of 55) or 37.5% (12 of 32) of patients with the Pro/Arg or Arg/Arg variant had a good pathologic response (P = 0.019). Moreover, patients with the Pro/Pro variant were more likely to have a positive axillary lymph node status than those with the Pro/Arg or Arg/Arg variant (P = 0.007). Furthermore, in multivariate analysis, p53 codon 72 polymorphism was found to be a strong predictor of pathologic response (odds ratio 6.7, 95% confidence interval, 1.4-31.2; P = 0.016). CONCLUSION: Our study indicates that breast cancer patients with the Pro/Pro variant may be less sensitive to anthracycline-based treatment than those with the Pro/Arg or Arg/Arg variant and suggests that analysis of p53 codon 72 polymorphism may provide a simple predictive marker for selecting the right breast cancer patients to anthracycline-based neoadjuvant chemotherapy in clinical setting.

Adult↗
PubMed2005

Comparison of codon usage measures and their applicability in prediction of microbial gene expressivity.

BACKGROUND: There are a number of methods (also called: measures) currently in use that quantify codon usage in genes. These measures are often influenced by other sequence properties, such as length. This can introduce strong methodological bias into measurements; therefore we attempted to develop a method free from such dependencies. One of the common applications of codon usage analyses is to quantitatively predict gene expressivity. RESULTS: We compared the performance of several commonly used measures and a novel method we introduce in this paper--Measure Independent of Length and Composition (MILC). Large, randomly generated sequence sets were used to test for dependence on (i) sequence length, (ii) overall amount of codon bias and (iii) codon bias discrepancy in the sequences. A derivative of the method, named MELP (MILC-based Expression Level Predictor) can be used to quantitatively predict gene expression levels from genomic data. It was compared to other similar predictors by examining their correlation with actual, experimentally obtained mRNA or protein abundances. CONCLUSION: We have established that MILC is a generally applicable measure, being resistant to changes in gene length and overall nucleotide composition, and introducing little noise into measurements. Other methods, however, may also be appropriate in certain applications. Our efforts to quantitatively predict gene expression levels in several prokaryotes and unicellular eukaryotes met with varying levels of success, depending on the experimental dataset and predictor used. Out of all methods, MELP and Rainer Merkl's GCB method had the most consistent behaviour. A 'reference set' containing known ribosomal protein genes appears to be a valid starting point for a codon usage-based expressivity prediction.

Chi-Square Distribution↗
PubMed2006

An overabundance of phase 0 introns immediately after the start codon in eukaryotic genes.

BACKGROUND: A knowledge of the positions of introns in eukaryotic genes is important for understanding the evolution of introns. Despite this, there has been relatively little focus on the distribution of intron positions in genes. RESULTS: In proteins with signal peptides, there is an overabundance of phase 1 introns around the region of the signal peptide cleavage site. This has been described before. But in proteins without signal peptides, a novel phenomenon is observed: There is a sharp peak of phase 0 intron positions immediately following the start codon, i.e. between codons 1 and 2. This effect is seen in a wide range of eukaryotes: Vertebrates, arthropods, fungi, and flowering plants. Proteins carrying this start codon intron are found to comprise a special class of relatively short, lysine-rich and conserved proteins with an overrepresentation of ribosomal proteins. In addition, there is a peak of phase 0 introns at position 5 in Drosophila genes with signal peptides, predominantly representing cuticle proteins. CONCLUSION: There is an overabundance of phase 0 introns immediately after the start codon in eukaryotic genes, which has been described before only for human ribosomal proteins. We give a detailed description of these start codon introns and the proteins that contain them.

Animals↗
PubMed2005

A polymorphism at codon 31 of gene p21 is not associated with primary open angle glaucoma in Caucasians.

BACKGROUND: Primary open angle glaucoma (POAG) is considered to be a neurodegenerative optic neuropathy, in which cell death occurs by apoptosis. p21, is an important protective component of the apoptotic pathway, regulating cellular arrest in the presence of DNA damage. An unstable or altered p21 protein could modify the cellular response to genomic injury and abolish the effect of p21. A previous study on a Chinese cohort suggested that the p21 codon 31 polymorphism may alter the state of apoptosis in glaucomatous optic neuropathy, failing to protect the ganglion cells. The aim of this study was to test the hypothesis that a p21 codon 31 polymorphism is associated with POAG on a Caucasian cohort. METHODS: 140 POAG patients and a control group of 73 healthy individuals were included in the study. All the subjects were of Caucasian origin. Genomic DNA was amplified by polymerase chain reaction, followed by enzymatic restriction fragment length polymorphism technique (PCR-RFLP). Patients and controls were genotyped for a single nucleotide polymorphism (C/A transversion) in the third base of codon 31 of p21, which leads to a serine (Ser)/arginine (Arg) substitution. RESULTS: The distribution of the genotypes in the POAG patients showed 128 (91.4%) Ser homozygotes, 10 (7.1%) Ser/Arg heterozygotes and 2 (1.5%) Arg homozygotes. In the control cohort, there were 61 (83.6%) Ser homozygotes and 12 (16.4%) Ser/Arg heterozygotes. No Arg homozygotes were present amongst the control group. Both the allelic and genotypic frequencies of the Ser or Arg residues at codon 31 were not significantly different between POAG patients and controls (Fisher's exact test, P = 0.20 for alleles and P = 0.0561 for genotypes). CONCLUSION: This study suggests that the p21 codon 31 polymorphism does not contribute to the risk of POAG in the Caucasian population.

Aged↗
PubMed2002

Preferred codons and amino acid couples in hyperthermophiles.

BACKGROUND: Most organisms grow at temperatures from 20 to 50 degrees C but some prokaryotes, including Archaea and Bacteria, are capable of withstanding higher temperatures, from 60 to >100 degrees C. What makes these cells so resistant to heat? Their biomolecules must be sufficiently stable, especially proteins, to work under these extreme conditions, but the bases for thermostability remains elusive. RESULTS: The preferential usage of certain couples of amino acids and codons in thermal adaptation was investigated, by comparative proteome analysis, using 28 complete genomes from 18 mesophiles, 4 thermophiles, and 6 hyperthermophiles. In the hyperthermophiles proteomes, whenever the percent of Glu (E) and Lys (K) Increased, the percent of Gln (Q) and His (H) decreased, so that the E+K/Q+H ratio was > 4,5; in the mesophiles proteomes, it was < 2,5 and in the thermophiles an intermediary value was observed. The E+K/Q+H ratios for chaperonins, potentially thermostable proteins, were higher than their proteome ratios whereas, for DNA ligases, not necessarily thermostable, they followed the proteome ones. Analysis of codon usage revealed that hyperthermophiles preferred AGR codons for Arg in detriment of CGN codons, which were preferred by mesophiles. CONCLUSIONS: The results suggested that the E+K/Q+H ratio may provide a useful mark for distinguishing hyperthermophilic, thermophilic and mesophilic prokaryotes and that the high percent of the amino acid couple E+K, consistently associated to the low percent of the pair Q+H, could contribute to protein thermostability. Second, the preference for AGR codons for Arg was a signature of all hyperthermophilics so far analyzed.

Amino Acids↗
PubMed1995

Three novel mutations of thyroid hormone receptor beta gene in unrelated patients with resistance to thyroid hormone: two mutations of the same codon (H435L and H435Q) produce separate subtypes of resistance.

We report three novel mutations of the thyroid hormone receptor beta (TR beta) gene in three unrelated Japanese patients with resistance to thyroid hormone (RTH). Patients A and B exhibited generalized resistance phenotype, while patient C displayed more pituitary-selective unresponsiveness. Direct sequencing of TR beta gene exon 10 disclosed novel point mutations in all three patients. A Phe to Ile (TTC-->ATC) substitution at codon 451, a His to Leu (CAT-->CTT) substitution at codon 435, and a His to Gln (CAT-->CAA) substitution at codon 435 were identified in patients A, B, and C, respectively. Sequencing of TR beta gene exons 5-9 as well as TR alpha gene exons 4-9 failed to detect any additional mutations. All three patients were heterozygous for respective mutations. The unaffected parents of patients A and B, having normal thyroid function, possessed no mutations of TR beta gene exon 10, indicating that the F451I and H435L mutations occurred de novo. The F451I mutation is located near the most frequent mutation site in the ligand 2 subdomain. The identical codon mutations H435L and H435Q, which lie at the extreme carboxyl-terminus of the dimerization subdomain near the 9th heptad, were found in clinically different subtypes of RTH: patient B with generalized resistance and patient C with pituitary-selective resistance, respectively. The mutations broaden the growing catalogue of the TR beta gene mutations that could cause different phenotypes, despite the defects at the same codon.

Adult↗
PubMed1998

Risk and penetrance of primary hyperparathyroidism in multiple endocrine neoplasia type 2A families with mutations at codon 634 of the RET proto-oncogene. Groupe D'etude des Tumeurs à Calcitonine.

Germline mutations of the RET proto-oncogene are responsible for multiple endocrine neoplasia type 2, including multiple endocrine type 2A (MEN 2A), type 2B (MEN 2B), and familial medullary thyroid carcinoma. The relationship between specific mutations and syndromic features has been established. In particular, the risk for pheochromocytoma and hyperparathyroidism (HPT) in MEN 2A patients is clearly associated with the presence of the RET mutation at a specific position, i.e. at codon 634. Also, a correlation between a specific mutation, C634R, and the development of HPT has been suggested but is still controversial. To further investigate the relationship between specific mutations of codon 634 and the development of HPT, we studied a population of 188 individuals, carrying mutations at codon 634, namely C634R (65 patients belonging to 10 families), C634Y (80 patients belonging to 11 families), or the less frequent codon 634 mutations [i.e. C634S, C634F, C634G, or C634W (43 patients belonging to 9 families)]. In this series of patients, we defined an overall HPT prevalence of 19.1% and found that this prevalence did not vary significantly, with respect to the nature of the mutation. However, irrespective of the particular mutation, the prevalence of HPT showed a high interfamilial variability. The statistical model that best fitted with the observed data was in favor of the heterogeneity of the risk for HPT, with 40% of the families showing an HPT risk of 34% and 60% of the families showing an HPT risk of 9%. In addition, our study clearly demonstrated that HPT could be an early component of the disease and provided the first estimate of age-specific and mutation-specific HPT penetrance in individuals with mutations of codon 634 of the RET proto-oncogene.

Adult↗
PubMed2025

Isolation of a novel human prion strain from a PRNP codon 129 heterozygous vCJD patient.

The epizootic prion disease of cattle, bovine spongiform encephalopathy (BSE), caused variant Creutzfeldt-Jakob disease (vCJD) in humans following dietary exposure. Codon 129 polymorphism of the human prion protein gene (PRNP), encoding either methionine (M) or valine (V), dictates the propagation of distinct human prion strains and up to now all but one neuropathologically confirmed vCJD patients have had a 129MM genotype. Concordant with this genetic association, transgenic modelling has established that human PrP 129V is incompatible with the vCJD prion strain and that depending on codon 129 genotype, primary human infection with BSE prions may, in addition to vCJD, result in sporadic CJD-like or novel phenotypes. In 2016 we saw the first neuropathologically confirmed case of vCJD in a patient with a codon 129MV genotype. This patient's neuropathology and molecular strain type were pathognomonic of vCJD but their clinical presentation and neuroradiological features were more typical of sporadic CJD, suggestive of possible co-propagation of another prion strain. Here we report the transmission properties of prions from the brain and lymphoreticular tissues of the 129MV vCJD patient. Primary transmissions into transgenic mice expressing human PrP with different codon 129 genotypes mainly produced neuropathological and molecular phenotypes congruent to those observed in the same lines of mice challenged with prions from 129MM vCJD patient brain, indicative that the vCJD prion strain was the dominant propagating prion strain in the patient's brain. Remarkably however, some transgenic mice challenged with 129MV vCJD patient brain propagated a novel prion strain type which at secondary passage was uniformly lethal in mice of all three PRNP codon 129 genotypes after similar short mean incubation periods. These findings establish that cattle BSE prions can trigger the co-propagation of distinct prion strains in humans.

Animals↗
PubMed2026

A rotavirus vaccine candidate attenuated by codon deoptimization protects neonatal mice against wild-type virus infection.

Rotavirus infection is a leading cause of acute viral gastroenteritis and diarrhea in infants and young children. Owing to the limited development of effective antiviral therapies, vaccination has become the primary and most efficient strategy to reduce rotavirus-associated morbidity and mortality. Compared with classical virus attenuation strategies, reverse genetics approaches such as codon deoptimization are safer, more time-saving, more cost-effective, and more controllable. The present study describes the development of an oral live-attenuated rotavirus vaccine candidate using codon deoptimization. Based on a simian rotavirus SA11 strain, eight gene segments, encoding the structural proteins VP1, VP2, VP3, and VP6, and the non-structural proteins NSP2, NSP3, NSP4, and NSP5, were subjected to codon deoptimization. Attenuated rotavirus by multi-segment codon deoptimization (MS8cd) exhibited markedly attenuated replication both in vitro and in vivo, attributable to reduced protein production independent of mRNA stability. Despite the attenuation, MS8cd elicited robust systemic and mucosal antibody responses which were sufficient to protect neonatal mice against challenge with wild-type rotavirus in a maternal immunization model. To alter the immunogenicity, MS8cd was manipulated to encapsidate outer capsid proteins of several prevalent human rotaviruses. These reassortants exhibited altered antigenic and immunogenic properties associated with the differing genotypes of the outer capsid proteins. In conclusion, this study describes the generation of promising rotavirus vaccine candidates attenuated by codon deoptimization. They are capable of eliciting genotype-specific and broad-spectrum protective immunity against circulating strains of rotavirus. This represents a rapid-response platform for the development of novel vaccines against emerging variants.

Animals↗
PubMed2005

X-linked genes evolve higher codon bias in Drosophila and Caenorhabditis.

Comparing patterns of molecular evolution between autosomes and sex chromosomes (such as X and W chromosomes) can provide insight into the forces underlying genome evolution. Here we investigate patterns of codon bias evolution on the X chromosome and autosomes in Drosophila and Caenorhabditis. We demonstrate that X-linked genes have significantly higher codon bias compared to autosomal genes in both Drosophila and Caenorhabditis. Furthermore, genes that become X-linked evolve higher codon bias gradually, over tens of millions of years. We provide several lines of evidence that this elevation in codon bias is due exclusively to their chromosomal location and not to any other property of X-linked genes. We present two possible explanations for these observations. One possibility is that natural selection is more efficient on the X chromosome due to effective haploidy of the X chromosomes in males and persistently low effective numbers of reproducing males compared to that of females. Alternatively, X-linked genes might experience stronger natural selection for higher codon bias as a result of maladaptive reduction of their dosage engendered by the loss of the Y-linked homologs.

Animals↗
PubMed2005

The incidence of genotypes at codon 171 of the prion protein gene (PRNP) in five breeds of sheep and production traits of ewes associated with those genotypes.

Scrapie is one of several transmissible spongiform encephalopathies of livestock. Disease susceptibility is linked to polymorphisms in the normal prion protein gene that encodes the mammalian prion precursor. Codon 171 of this gene is a major determinant of scrapie susceptibility. Selection for arginine (R) at codon 171 is encouraged by the USDA to decrease the incidence of scrapie. Objectives of this study were to determine the frequency of R allele variants at codon 171 in a sample of sheep from five breeds (Columbia, Hampshire, Rambouillet, Suffolk, and Targhee) and western white-faced commercial ewes and to determine whether the R allele is associated with ewe and lamb production traits. Genotyping was performed on 532 ewes and 901 lambs from the University of Wyoming flock, in addition to 820 rams from 52 sheep producers from Wyoming and surrounding areas, using a DNA mismatch assay that discriminated the R allele from others at codon 171. Genotyping was performed by DNA sequencing on 127 rams representing all breeds, except Hampshire from the USDA Sheep Experiment Station at Dubois, ID. The 171R allele was found in all five breeds and in the commercial western white-faced ewes. Genotype frequencies varied (P < 0.001) by breed in ewe and ram populations. Influence of R-allele frequency on ewe lambing records and individual lamb records was analyzed for Columbia (62, 161, 121), Hampshire (89, 193, 162), Rambouillet (87, 179, 133), Suffolk (67, 178, 161), and commercial sheep (227, 463, 324) for numbers of ewes, total number of ewe production records, and individual lamb records, respectively. Suffolk ewes without the R allele (non-R/non-R) gave birth to more (P or= 0.08) by ewe genotype. Lamb birth and weaning weights were not influenced (P >or= 0.12) by lamb genotype in any of the breeds or in the commercial flock. In this population, ultimate lamb production was only influenced by genotype at codon 171 in the Suffolk flock.

Animals↗
PubMed1993

Codon usage in mammalian genes is biased by sequence slippage mechanisms.

The codons for some conserved amino acids are found to be the same between homologous genes from different species when the statistics of codon usage would suggest that they should be different. I examine whether this 'coincidence' of codon usage could be due to genetic mechanisms homogenising the DNA around specific sites. This paper describes the further analysis of the coincident codons in 19 genes (a total of 96 homologues) for slippage. Coincident codons arise in contexts of increased sequence simplicity, and have a high chance of occurring within sequences similar to the recombination-prone minisatellite 'core' sequence. This suggests a role of genetic homogenisation in their generation.

Amino Acid Sequence↗
PubMed2006

Evaluation of p53 codon 72 polymorphism in adenocarcinomas of the colon and rectum in La Plata, Argentina.

AIM: To evaluate the potential association between p53 codon 72 polymorphism and sporadic colorectal adenocarcinoma development,and human papillomavirus (HPV) infection. METHODS: One-hundred and nine controls and 53 patients with colon cancer from the city of La Plata, Argentina were analyzed. p53 codon 72 genotypes and HPV infection were identified using allele-specific polymerase chain reaction and nested polymerase chain reaction, respectively. RESULTS: The differences in the distribution of p53 codon 72 polymorphism between the cases and controls were statistically significant. The arginine allele had a prevalence of 0.65 in controls and 0.77 in cases. The corresponding odds ratio for the homozygous arginine genotype was 2.08 (95% CI, 1.06-4.05; P<0.05). Lack of association was found between p53 polymorphism and HPV infection in the set of adenocarcinomas. CONCLUSION: The findings of the present study indicate that p53 codon 72 arginine homozygous genotype may represent a genetic predisposing factor for colon cancer development. However,further studies are needed in order to elucidate the role of p53 codon 72 polymorphism in colorectal cancer.

Adenocarcinoma↗
PubMed1997

Precore codon 28 stop mutation in hepatitis B virus from patients with hepatocellular carcinoma.

OBJECTIVES: Hepatitis B virus (HBV) with a stop mutation at precore codon 28 (TGG-->TAG, tryptophan-->stop) was investigated to clarify if such a mutant virus might play a role in hepatocarcinogenesis. METHODS: A total of 73 patients with HBV-related hepatocellular carcinoma were included in this study. Polymerase chain reaction (PCR) was performed in DNA samples extracted from 73 sera to amplify a HBV-DNA segment involving the precore and proximal core regions, and sequences of PCR products were analyzed to see the presence of the mutations at precore codon 28 by a direct sequencing method. RESULTS: HBV-DNA was detectable in 64 (88%) patients by PCR. The stop mutation at precore codon 28 was identified in 50 of 58 PCR products (86%), in which direct sequencing was performed. Among patients with this mutant HBV, 21/50 (42%) patients were co-infected with wild-type HBV. The mutant virus was found in 23/28 (82%) patients with hepatitis B e antigen (HBeAg) and 27/30 (90%) patients without HBeAg. The mutant HBV alone was found in 10/28 (36%) patients with HBeAg and 19/30 (63%) without HBeAg. Among those patients on whom laparoscopy was performed, 22/24 (92%) with the precore codon 28 stop mutant alone had cirrhosis, compared to 12/19 (63%) co-infected by both the mutant and the wild-type (p < 0.05). The association of this mutant virus with both the presence and absence of HBeAg, and its association with cirrhosis when there is no co-infection with wild-type HBV, suggests an evolving pattern of liver pathology. CONCLUSION: The high prevalence of a stop mutation at precore codon 28 in these patients with hepatocellular carcinoma suggests that HBV with this mutation may contribute to the development of hepatocellular carcinoma.

Adolescent↗
PubMedDate not supplied

RET germline mutation in codon 791 in a family representing 3 generations from age 5 to age 70 years: should thyroidectomy be performed?

OBJECTIVE: To describe a kindred with a rare RET germline mutation in codon 791 and discuss potential management strategies. METHODS: We present clinical and biochemical data as well as results of mutation analysis in our study subjects and provide an overview of related published reports. RESULTS: Multiple endocrine neoplasia type 2 (MEN 2) is a familial cancer syndrome characterized by the development of medullary thyroid carcinoma (MTC), pheochromocytoma, and parathyroid hyperplasia or adenoma. Germline mutations in RET are responsible for this autosomal dominant syndrome. Familial MTC is a variant of MEN 2A and can be caused by RET mutations in codon 791. Deaths from gene carriers with mutations in these codons have not yet been reported. In general, gene carriers with these RET mutations have late-onset MTC. Because only a few kindreds with this specific mutation have been identified and no long-term follow-up data are available, management of these patients can be a challenge. We illustrate the difficulties with decisions about not only when to perform thyroidectomy in these patients but also whether thyroidectomy should even be considered in such gene carriers with a benign course. Our reported kindred included four carriers with a codon 791 RET germline mutation, one of whom had the rare concomitant occurrence of acromegaly and MEN 2A. The 70-year-old mother had acromegaly and hyperparathyroidism but normal serum calcitonin levels and normal findings on thyroid ultrasound examination. She refused pentagastrin testing and any surgical intervention. The 37-year-old daughter had hypothyroidism, a small thyroid gland, and negative results of pentagastrin stimulation testing of calcitonin. The 18-year-old grandson also had a negative pentagastrin test result and normal thyroid ultrasound findings. The 5-year-old granddaughter had normal results of thyroid ultrasonography. In all patients, we recommended thyroidectomy. CONCLUSION: Prospective studies are needed to clarify which patients with codon 791 RET germline mutation should undergo thyroidectomy.

Acromegaly↗
PubMed2006

The rat ARF protein is translated from two closely spaced ATG start codons and can transcriptionally activate p53 in the absence of p53 protein stabilization.

We have analyzed the transcriptional start sites of the rat ARF gene and the amino acid sequence of the rat ARF tumor suppressor protein. The 5' end of the ratARF gene is similar to that of a number of cellular housekeeping genes in that it is CG-rich and does not contain an upstream TATA box motif to define a precise transcriptional start site. The transcription of the rat ARF gene is initiated at multiple start sites with one major start site accounting for 41% of transcription. The rat ARF protein contains two methionine ATG codons at its amino terminus separated by 10 amino acids. The translation of the major endogenous ARF protein species is initiated from the upstream methionine ATG codon. The upstream methionine ATG codon is predominantly used, despite the fact that it is both very close to the major transcriptional start site (6 bases downstream) and is in a less favorable nucleic acid sequence context than the downstream ATG, relative to the ideal sequence postulated for efficient initiation of translation. The downstream, inefficient rat ARF ATG is equivalent to the major mouse ARF ATG start codon. Both of these closely spaced ATGs can be utilized as a translational start codon to produce a nucleolar-localized ARF protein which can induce a p53-dependent inhibition of cell division and transcriptional activation of p53 in the absence of p53 stabilization.

Amino Acid Sequence↗
PubMed1996

Predictive value of codon 215 reverse transcriptase mutation on the efficacy of didanosine in HIV-infected, zidovudine-experienced patients.

We investigated whether or not mutations at codon 215 in the HIV reverse-transcriptase-encoding gene predicted a lower efficacy of didanosine therapy, as defined by survival of patients and change in CD4 cell counts in 121 HIV-infected, zidovudine-experienced patients. A trend for shorter survival, although not reaching significance, was observed for patients with HIV strains with the reverse transcriptase codon 215 mutation (P = 0.07), but this trend disappeared after adjustment for initial CD4 cell counts. During the first 3 months on didanosine therapy, the increase in CD4 cell counts was greater in patients who were wild type at codon 215 than in those with the mutation at codon 215 (P = 0.03). These data suggest that there was a better initial CD4 response to didanosine therapy in patients with HIV without the mutation at codon 215, but that this response did not translate into increased survival.

Anti-HIV Agents↗
PubMed2002

DNA repair gene XRCC3 codon 241 polymorphism, its interaction with smoking and XRCC1 polymorphisms, and bladder cancer risk.

DNA repair efficiency varies among individuals, with reduced repair capacity as a risk factor for various cancers. This variability could be partly explained by allelic variants for different DNA repair genes. We examined the role of a common polymorphism in the XRCC3 gene (codon 241: threonine to methionine change) and bladder cancer risk. This gene plays a role in the homologous recombination pathway, which repairs double-strand breaks. The functional consequences of the XRCC3 codon 241 polymorphism are still unknown. We hypothesized that this polymorphism could affect repair of smoking-associated DNA damage and could thereby affect bladder cancer risk. We genotyped 233 bladder cancer cases and 209 controls who had been frequency matched to cases on age, sex, and ethnicity. We observed little evidence of a positive association between subjects who carried at least one copy of the codon 241 Met allele and bladder cancer (odds ratio: 1.3; 95% confidence interval: 0.9-1.9). Among heavy smokers, individuals with the Met allele had about twice the risk of those without it; however, a test of interaction was not statistically significant (P = 0.26). Previously, we observed in these subjects an association between bladder cancer risk and allelic variants of the XRCC1 gene, which is involved in the repair of base damage and single-strand breaks. In this study, we found some evidence for a gene-gene interaction between the XRCC1 codon 194 and XRCC3 codon 241 polymorphisms (P = 0.09) and some support for a possible gene-gene-smoking three-way interaction (P = 0.08).

Codon↗