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At least 649 records · Page 36Linked to original sources
PubMed1993

Site-directed and deletion mutational analysis of the receptor binding domain of the interleukin-6 receptor targeted fusion toxin DAB389-IL-6.

We have used site-directed and in-frame deletion mutational analysis in order to explore the structural features of the IL-6 portion of the diphtheria toxin-related interleukin-6 (IL-6) fusion toxin DAB389-IL-6 that are essential for receptor-binding and subsequent inhibition of protein synthesis in target cells. Deletion of the first 14 amino acids of the IL-6 component of the fusion toxin did not alter either receptor binding affinity or cytotoxic potency. In contrast, both receptor binding and cytotoxic activity were abolished when the C-terminal 30 amino acids of the fusion toxin were deleted. In addition, we explored the relative role of the disulfide bridges within the IL-6 portion of DAB389-IL-6 in the stabilization of structure required for receptor-binding. The analysis of mutants in which the substitution of either Cys440, Cys446, Cys469 or Cys479 to Ser respectively, demonstrates that only the disulfide bridge between Cys469 and Cys479 is required to maintain a functional receptor binding domain. In addition, the internal in-frame deletion of residues 435-451, which includes Cys440 and Cys446, was found to reduce, but not abolish receptor binding affinity. These results further demonstrate that the disulfide bridge between Cys440 and Cys446 is not essential for receptor-binding. However, the reduced cytotoxic potency of DAB389-IL6(delta 435-451) suggests that the conformation and/or receptor binding sites associated with this region of the fusion toxin is/are important for maintaining the wild type receptor binding affinity and cytotoxic potency.

Base Sequence↗
PubMed1993

Mutational analysis of G protein alpha subunit G(o) alpha expressed in Escherichia coli.

G protein-mediated signal transduction is dependent on alpha subunit interactions with beta gamma subunits, receptors, effectors, magnesium ions, and guanine nucleotides. The interdependence of these interactions can be probed by mutational analysis. We developed large scale screening procedures in recombinant Escherichia coli to identify and characterize novel mutations in G(o) alpha. Random mutations were generated by polymerase chain reaction in the amino-terminal 56 amino acids of G(o) alpha. Guanine nucleotide binding properties of the mutants were assayed in situ and in crude extracts of recombinant E. coli. beta gamma interactions were assayed by pertussis toxin mediated ADP-ribosylation. Efficacy of the screening procedures was evaluated by studying properties of wild-type G(o) alpha and site-directed mutations that were characterized previously in other G proteins. Several novel mutants with altered GTP binding characteristics and reduced ability to interact with beta gamma had been isolated from the randomly generated mutant library. ADP-ribosylation of mutants R10G, K21N, and K35E was significantly reduced, whereas two of the mutants bearing multiple amino acid substitutions were refractory to modification. Mutant K35E also exhibited reduced affinity to guanosine 5'-(3-O-thio)triphosphate at submicromolar concentrations of magnesium. These experiments demonstrate the feasibility of using large scale random mutagenesis in the studies of G protein function.

Adenosine Diphosphate Ribose↗
PubMed2004

The necessity of complete CFTR mutational analysis of an infertile couple before in vitro fertilization.

OBJECTIVE: To determine the genotype of a triplet resulted from an IVF procedure, with discordant cystic fibrosis (CF) phenotype. DESIGN: Molecular diagnosis of CF. SETTING: Affected triplet followed at the CF Clinic Center of Children's Hospital Los Angeles was referred to Molecular Genetics Laboratory at Georgetown University Medical Center for comprehensive DNA analysis of the cystic fibrosis transmembrane regulator (CFTR) gene. PATIENT(S): Three affected children and the healthy parents with negative family history of CF. MAIN OUTCOME MEASURE(S): Temporal temperature gradient gel electrophoresis and direct DNA sequencing were used to detect and to identify the mutations. RESULT(S): The child with classic CF had DeltaF508 and R553X mutations. Two children with mild CF symptoms had DeltaF508 and R117C. The father carried two mutations, R553X and R117C. The mother is a carrier for DeltaF508. CONCLUSION(S): Mutational analysis of the CFTR gene should always be recommended to the infertile couples seeking for IVF. The CFTR mutation screening would be essential if the man has congenital bilateral absence of vas deferens (CBAVD) despite the negative family history of CF. Option of complete CFTR gene analysis at a cost of about 1,500-2,000 dollars should be made available if one mutation is found in the male partner with congenital bilateral absence of vas deferens.

Adult↗
PubMed2006

Emergence of ofloxacin resistance in Mycobacterium tuberculosis clinical isolates from China as determined by gyrA mutation analysis using denaturing high-pressure liquid chromatography and DNA sequencing.

A high rate of double point mutations in gyrA (56% of 87 ofloxacin-resistant Mycobacterium tuberculosis clinical isolates) indicates the emergence of fluoroquinolone resistance. This is the first report to describe denaturing high-pressure liquid chromatography analysis of mutations in gyrA of M. tuberculosis in a large number of clinical isolates.

Anti-Bacterial Agents↗
PubMed2000

Characterization of the human complex I NDUFB7 and 17.2-kDa cDNAs and mutational analysis of 19 genes of the HP fraction in complex I-deficient-patients.

Deficiency of NADH:ubiquinone oxidoreductase, the first enzyme complex of the mitochondrial respiratory chain, is one of the most frequent causes of human mitochondrial encephalomyopathies. A relatively small percentage of human complex I deficiency is associated with mitochondrial DNA mutations. cDNA characterization and mutational analysis of the structural complex I genes in 19 complex I-deficient patients, in whom common mtDNA mutations have been excluded, has so far revealed five patients with alterations in evolutionary conserved nuclear-encoded proteins. In order to complete our knowledge about the expected 36 structural nuclear complex I genes, we characterized the NDUFB7 and the 17.2-kDa cDNA sequences of the hydrophobic (HP) fraction of the complex. Subsequently, we screened all subunits of this fraction for the presence of mutations in those 14 patients of our initial patient cohort in whom the underlying genetic cause had not been elucidated. Strikingly, no pathogenic mutations were found in the HP subunits that would explain the complex I deficiency in our patients. Other strategies are needed to unravel proteins involved in the pathogenesis of the complicated cellular network of transcription until correct assemblage of complex I.

Amino Acid Sequence↗
PubMed1997

First prenatal diagnosis by mutation analysis in a family with Sjögren-Larsson syndrome.

Sjögren-Larsson syndrome (SLS) is a rare, autosomal recessive disorder characterized by congenital ichthyosis, mental retardation, and spastic diplegia or tetraplegia. The disorder has the highest incidence in the north of Sweden and most of the cases are caused by a C943T mutation in the FALDH gene. Prenatal diagnosis and PCR-based mutation analysis was performed in a pregnancy where the parents are heterozygous carriers for this mutation. The fetus was found to be homozygous for the mutation and thus affected by SLS.

Abortion, Induced↗
PubMed2001

Mutational analysis of zinc resistance in Pseudomonas putida strain S4.

The genes for resistance to any essential metal ion are generally tightly regulated. In Pseudomonas putida strain S4, a multiple metal-resistant strain, mutational analysis gave strong evidence to the presence of the same for the expression of Zn resistance. Zn-sensitive mutants showed a lower MTC of Zn and expressed the Zn resistance genes with a lower efficacy. Non-complementation between these mutants suggests that they are possibly involved in the same function. Altered response to Zn of these mutants assisted in predicting the involvement of a repressor protein regulating the expression of Zn resistance genes. Zn hypersensitive mutant, on the other hand, appears to have an unregulated Zn uptake. This seems to provide the sensor component in the regulation. Zn resistance in strain S4 consists of three steps, viz., uptake, efflux, and binding, which are shared by a Zn homeostasis mechanism as well.

Bacterial Proteins↗
PubMed2004

A multistep model for ovarian tumorigenesis: the value of mutation analysis in the KRAS and BRAF genes.

Epithelial ovarian tumours represent a complex group of histological subtypes and there has long been controversy over the question of a precursor lesion for these neoplasms. The application of mutation analysis of the KRAS and BRAF genes (members of the RAS-RAF-MEK-ERK-MAP kinase pathway) is consistent with the model for progression of mucinous carcinomas and a subset of serous carcinomas (the so-called low-grade serous carcinomas) through benign and borderline lesions. The relatively high incidence of BRAF and KRAS mutations in serous borderline tumours and low-grade serous carcinomas, and their extremely low incidence/absence in high-grade serous carcinomas, provide strong evidence that high-grade carcinomas do not arise through this intermediate step.

Cystadenoma, Serous↗
PubMed2006

Iron overload and prolonged ingestion of iron supplements: clinical features and mutation analysis of hemochromatosis-associated genes in four cases.

We evaluated and treated four white adults (one man, three women) who had iron overload associated with daily ingestion of iron supplements for 7, 15, 35, and 61 years, respectively. We performed HFE mutation analysis to detect C282Y, H63D, and S65C in each patient; in two patients, HFE exons were sequenced. In two patients, direct sequencing was performed to detect coding region mutations of TFR2, HAMP, FPN1, HJV, and ALAS2. Patients 1-4 ingested 153, 547, 1,341, and 4,898 g of inorganic iron as supplements. Patient 1 had hemochromatosis, HFE C282Y homozygosity, and beta-thalassemia minor. Patient 2 had spherocytosis and no HFE coding region mutations. Patient 3 had no anemia, a normal HFE genotype, and no coding region mutations in HAMP, FPN1, HJV, or ALAS2; she was heterozygous for the TFR2 coding region mutation V583I (nt 1,747 G-->A, exon 15). Patient 4 had no anemia and no coding region mutations in HFE, TFR2, HAMP, FPN1, HJV, or ALAS2. Iron removed by phlebotomy was 32.4, 10.4, 15.2, and 4.0 g, respectively. There was a positive correlation of log(10) serum ferritin and the quantity of iron removed by phlebotomy (P = 0.0371). Estimated absorption of iron from supplements in patients 1-4 was 20.9%, 1.9%, 1.1%, and 0.08%. We conclude that the clinical phenotypes and hemochromatosis genotypes of adults who develop iron overload after ingesting iron supplements over long periods are heterogeneous. Therapeutic phlebotomy is feasible and effective, and would prevent complications of iron overload.

Adult↗
PubMed1998

Cloning, genomic organization, alternative transcripts and mutational analysis of the gene responsible for autosomal recessive universal congenital alopecia.

Complete or partial congenital absence of hair (congenital alopecia) may occur isolated or with associated defects. The majority of families with isolated congenital alopecia has been reported to follow an autosomal recessive mode of inheritance (MIM 203655). We have previously mapped the gene for autosomal recessive congenital alopecia in a large inbred Pakistani family in which affected persons show complete absence of hair development (universal congenital alopecia) to a 15 cM region on chromosome 8p21-22. Here we report the cloning and characterization of the human homologue of the mouse hairless gene and show that it is located in the critical region on chromosome 8p21-22. Determining the exon-intron structure allowed detailed mutational analysis of DNA samples of patients with universal congenital alopecia. We detected a homozygous missense mutation in the Pakistani family and a homozygous splice donor mutation in a family from Oman. In addition, we show that the human hairless gene undergoes alternative splicing and that at least two isoforms generated by alternative usage of exon 17 are found in human tissues. Interestingly, the isoform containing exon 17 is the predominantly expressed isoform in all tissues but skin, where exclusive expression of the shorter isoform was observed. We speculate that this tissue-specific difference in the proportion of hairless transcripts lacking exon 17 sequences could contribute to the tissue-specific disease phenotype observed in individuals with isolated congenital alopecia.

Adult↗
PubMed2004

Elusive amines and cluster headache: mutational analysis of trace amine receptor cluster on chromosome 6q23.

Cluster headache (CH) is characterised by unilateral pain and ipsilateral autonomic features. To date, no molecular genetic evidence has been shown for CH. Small pedigrees and low penetrance render the identification of the CH-gene quite difficult. Nonetheless the association of CH and migraine to a new class of amine, namely trace or elusive amines such as tyramine, octopamine and synephrine, has recently been demonstrated. In particular, in comparison to healthy control subjects, all these neurotransmitters have been found to be greatly elevated in CH sufferers in plasma and platelets both in active and remission periods. A cluster of gene-encoding G-protein-coupled receptors that bind and are activated by trace amines was identified in the long arm of chromosome 6q23. We evaluated two families with CH by linkage analysis to 6q23 region and the mutation scanning of the TAR 1, TAR 3, TAR 4, TAR 5, PNR and GPR58 genes by denaturing high liquid chromatography is in progress in 16 familial cases.

Biogenic Amines↗
PubMed1995

Mutational analysis of the CDKN2 (MTS1/p16ink4A) gene in primary B-cell lymphomas.

The CDKN2 gene located on chromosome 9p21 encodes the cyclin-dependent kinase-4 inhibitor p16. This gene is a putative tumor-suppressor gene because of its frequent alterations in many kinds of tumor cell lines. We analyzed the CDKN2 gene to evaluate its alterations in 52 primary specimens of non-Hodgkin's lymphoma (NHL) or chronic lymphocytic leukemia (CLL) of B-cell origin by Southern blot analysis, polymerase chain reaction-mediated single-strand conformation polymorphism (PCR-SSCP) analysis, and direct sequencing. By Southern blot analysis, we showed homozygous deletion of the CDKN2 gene in 3 of 42 patients with B-NHL (7.1%). After screening by PCR-SSCP analysis, direct sequencing identified one missense mutation at codon 72 (nucleotide 233) and two frameshifts due to a 35-bp deletion arising at codon 49 (nucleotides 163 to 175) in patients with B-NHL (3 of 42, 7.1%). In the patient carrying the missense mutation, hemizygous deletion of the CDKN2 gene was also suspected. In this study, we detected alterations in CDKN2 in 6 of 42 patients (14.3%) with B-NHL and in none of 10 patients with B-CLL. Our results suggest that the CDKN2 alterations contribute in tumorigenesis in some patients with B-NHL.

Adolescent↗
PubMed1994

Breakpoint cluster region gene product-related domain of n-chimaerin. Discrimination between Rac-binding and GTPase-activating residues by mutational analysis.

The breakpoint cluster region gene product (Bcr) is a GTPase-activating protein (GAP) for members of the Rho family, Cdc42Hs, and Rac1, as is the brain protein n-chimaerin. At least 15 proteins have sequence identity to the GAP domain (150 amino acid residues) of Bcr. The widespread occurrence of proteins that possess sequence identity to the Bcr-related GAP domain makes it especially important to understand its structure/function relationships. Amino acid sequence alignment of these proteins reveals three blocks of conservation in the GAP domain. Here, we present a mutational analysis of this domain using n-chimaerin sequences. Ten mutations were constructed (at least two in each of the blocks of conservation), expressed as glutathione S-transferase fusion proteins in Escherichia coli, and purified. Seven of the mutants, including deletions, still possessed GAP activity for Rac1. Three of the mutants had no Rac1-GAP activity but were still able to bind Rac1. IC50 values obtained from competition experiments suggest that n-chimaerin and the mutants with no GAP activity bound Rac1 with similar apparent binding constants. Thus, this mutant analysis allows discrimination between Rac1-binding and Rac1 GTPase- activating residues.

Amino Acid Sequence↗
PubMed2000

Mutation analysis of P73 and TP53 in Merkel cell carcinoma.

The p73 gene has been mapped to 1p36.33, a region which is frequently deleted in a wide variety of neoplasms including tumours of neuroectodermal origin. The p73 protein shows structural and functional homology to p53. For these reasons, p73 was considered as a positional and functional candidate tumour suppressor gene. Thus far, mutation analysis has provided no evidence for involvement of p73 in oligodendrogliomas, lung carcinoma, oesophageal carcinoma, prostatic carcinoma and hepatocellular carcinoma. In neuroblastoma, two mutations have been observed in a series of 140 tumours. In view of the occurrence of 1p deletions in Merkel cell carcinoma (MCC) and the location of p73 we decided to search for mutations in the p73 gene in five MCC cell lines and ten MCC tumours to test potential tumour suppressor function for this gene in MCC. In view of the possible complementary functions of p73 and TP53 we also examined the status of the TP53 gene. Sequence analysis of the entire coding region of the p73 gene revealed previously reported polymorphisms in four MCCs. In one MCC tumour, a mis-sense mutation located in the NH2-terminal transactivation region of the p73 gene was found. These results show that p73, analogous to neuroblastoma, is infrequently mutated in MCC. This is also the first report in which the role of TP53 in MCC has been investigated by sequencing the entire coding region of TP53. TP53 mis-sense mutations and one non-sense mutation were detected in three of 15 examined MCCs, suggesting that TP53 mutations may play a role in the pathogenesis or progression of a subset of MCCs. Moreover, typical UVB induced C to T mutations were found in one MCC cell line thus providing further evidence for sun-exposure in the aetiology of this rare skin cancer.

Base Sequence↗
PubMed1987

Importance of HLA-DQ and -DP restriction elements in T-cell responses to soluble antigens: mutational analysis.

We describe a new approach to delineating the restriction elements used by antigen-specific human T-cell lines. EBV-transformed B cell lines and congenic HLA class II antigen-loss mutants are used to present soluble antigen to immune T cells. In this way it is possible to assess the independent contribution of individual class II loci to the restriction repertoire of the T cells. In contrast to results obtained with other methods of restriction element analysis, we find that approximately 40% of the T-cell response to several antigens is restricted by non-DR class II molecules. Both mutational analysis and blocking by class II specific monoclonal antibodies demonstrate that the non-DR restricted responses derive from DQ and DP-encoded determinants. We also find specific DR/DQ haplotype preferences for the presentation of some but not all antigens. Using a mutant that expresses only the DQ1 molecule, and is derived from a DR1, DQ1 parent line, we demonstrate a functional split of serologically defined DQ1 molecules consistent with the electrophoretic variation reported between DQ1 molecules linked to DR1 and those linked to DR2. Pairs of mutants that differ by expression of a single class II protein reveal a much broader use of available class II restriction elements than previously recognized.

Antibodies, Monoclonal↗
PubMed2001

Methylation and mutational analysis of p27(kip1) in prostate carcinoma.

BACKGROUND: We have previously identified 12p12-13 as a region of frequent genetic loss in prostate carcinoma. A candidate tumor suppressor gene at this locus is the cyclin dependent kinase inhibitor p27(kip1), which has been implicated as a marker of aggressive prostate carcinoma. Herein, we examine metastatic prostate tumors, xenografts, and cell lines for gene inactivation via mutational inactivation or promoter hypermethylation. METHODS: Mutation analysis was performed on metastatic prostate tumors of 18 patients, eight prostate carcinoma cell lines, and 18 xenografts by PCR amplification of the entire open reading frame of p27(kip1). PCR products were sequenced directly using internal primers. Methylation analysis was performed on four cell lines and nine xenografts using direct sequencing of cloned PCR products of bisulfite treated DNA. Presence of a CpG was consistent with methylation of that cytosine in the original sample. RESULTS: With the exception of the previously reported homozygous deletion, no additional mutations were identified. Methylated CpG residues were identified in three xenografts (LuCAP23, LuCAP35, and PC82) and the methylated residues clustered at six sites; the cytosines 69, 149, 191, 286, 349, and 487 base pairs 5' of the ATG start codon. However, no sample demonstrated promotor methylation in all sequenced clones and the number of methylated base pairs ranged from seven to three, not the level usually associated with gene silencing. CONCLUSIONS: Mutational inactivation of p27(kip1) is a rare event in metastatic prostate carcinoma. While CpG methylation does occur, it is an infrequent event and does not appear to be the mechanism of p27(kip1) down regulation in prostate carcinoma.

Cell Cycle Proteins↗
PubMed2004

Mutation analysis of the multidrug resistance protein 2 (MRP2) gene in a Japanese patient with Dubin-Johnson syndrome.

Dubin-Johnson syndrome (DJS) is a recessive inherited disorder with conjugated hyperbilirubinemia caused by a dysfunction of multidrug resistance protein 2 (MRP2) on the canalicular membrane of hepatocytes. A mutational analysis of the MRP2 gene was carried out in a Japanese female with DJS. In this patient, we found a homozygous 2125T > C mutation in exon 17. This mutation affects the conversion of tryptophan(709) to arginine(709) (W709R) in the first ATP-binding cassette in the MRP2 protein. It was concluded that this homozygous mutation of the MRP2 gene contributed to the induction of hyperbilirubinemia in this case.

Journal Article↗