Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Point Mutation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,639 records · Page 91Linked to original sources
PubMed1989

A deletion of the PDC1 gene for pyruvate decarboxylase of yeast causes a different phenotype than previously isolated point mutations.

We deleted most of the pyruvate decarboxylase structural gene PDC1 from the genome of Saccharomyces cerevisiae. Surprisingly, mutants carrying this deletion allele showed a completely different phenotype than previously described point mutations. They were able to ferment glucose and their specific pyruvate decarboxylase activity was only reduced to 45% of the wild type level. Northern blot analysis revealed that a sequence in the yeast genome homologous to PDC1 and formerly designated as a possible pseudogene is expressed and may code for a different but closely related pyruvate decarboxylase. The products of the two PDC genes seem to form hybrid oligomers, however both homooligomers have enzyme activity. Thus, the product of the PDC1 gene is not absolutely necessary for glucose fermentation in yeast.

Blotting, Southern↗
PubMed1978

Mutagenicity of industrial compounds. VII. Styrene and styrene oxide: II. Point mutations, chromosome aberrations and DNA repair induction analyses.

The possible genetic effects produced by styrene have been investigated by means of different methodologies in several biological organisms: (a) the induction of point mutation has been investigated in Salmonella typhimurium (reverse mutation), in the yeast Schizosaccharomyces pombe (forward mutation), both in vitro and in vivo, in the host-mediated assay of mice, and in the Chinese hamster cell line grown in vitro (V-79) (forward mutation); (b) the induction of chromosome mutation has been investigated in vivo, in mice, through the analysis of the presence of chromosome aberrations in bone marrow cells of treated animals; (c) the production of DNA (deoxyribonucleic acid) damage and the stimulation of DNA repair synthesis have been evaluated from measurements of unscheduled DNA synthesis in a heteroploid human cell line (EUE) and gene-conversion produced in the yeast Saccharomyces cerevisiae treated in vitro and in vivo (host-mediated assay). All the in vitro studies have been developed by the testing of the styrene in the presence of a metabolic activating system obtained with a mouse liver microsomal preparation. Styrene oxide, one of the in vivo metabolites of styrene with electrophilic properties towards DNA molecules, have also been tested in similar systems. Styrene was not mutagenic in all the systems tested; styrene oxide, on the contrary, was shown to be an active mutagen, independently of the genetic system under evaluation.

Animals↗
PubMed1994

Detection of two point mutations causing familial defective apolipoprotein B-100 by heteroduplex analysis.

Familial defective apolipoprotein B-100 (FDB) is a dominantly-inherited genetic disorder causing primary hypercholesterolemia and premature coronary heart disease. To date, only two mutations causing FDB have been identified. A rapid non-radioactive technique is described to detect both disease-related apolipoprotein B point mutations in polymerase chain reaction (PCR) products amplified from genomic DNA. Heteroduplex formation between different alleles from FDB heterozygotes was shown to be visible directly after electrophoresis of PCR products and staining in low cross-linking polyacrylamide gels. We found that the simplicity of the method, in addition to its potential to identify new mutations in the amplified PCR product, makes heteroduplex detection the preferred initial method of screening potential heterozygotes.

Apolipoprotein B-100↗
PubMed1990

Evolution of protein cores. Constraints in point mutations as observed in globin tertiary structures.

The amino acid sequences of ten globin chain tertiary structures were aligned and structurally equivalenced by spatial superposition of main-chain C alpha atoms. A search was then performed for structurally equivalent residue pairs that were buried in the protein core and that had mutated but maintained similar unmutated environments. Residues with atoms in contact with such central residue pairs define their environments. Such examples of point mutations would represent in vivo site-directed mutagenesis as would be observed in evolution. A search for mutated but exposed equivalent central residues was also performed. The constraints placed on the characteristics of the mutated residues (e.g., side-chain volume, polarity, radius of gyration) allow suggestions for the evolutionary modes of protein core and surface development as well as residue substitution guidelines to maintain structural stability in protein engineering and design.

Amino Acid Sequence↗
PubMed1991

Unexpected point mutations activate cryptic 3' splice sites by perturbing a natural secondary structure within a yeast intron.

The 3' splice site of the budding yeast Kluyveromyces lactis actin gene (ACT) intron is distally spaced (122 nucleotides) from its branchpoint and is also preceded by a silent PyAG located 43 nucleotides upstream. We devised a genetic screen that resulted in the isolation of several randomly induced cis-acting mutations that activate the silent PyAG as a 3' splice site. These mutations fall within a region surrounding this PyAG, which can hypothetically fold into a higher-order structure. Site-directed mutational analyses demonstrate that a hairpin structure in this region is required for correct 3' splice-site selection. Analysis of the point mutations suggests that local breathing of the hairpin near the first PyAG can lead to its activation. These data demonstrate that 3' splice-site selection is not a consequence of a linear, directional scanning mechanism, but support the notion of a critical positioning requirement for 3' splice-site selection. We speculate on the possible origin of this intron-encoded structural motif, which has homology to a bacterial transposon and suggests one possible origin for alternative splicing mechanisms in higher eukaryotes.

Base Composition↗
PubMed1994

A Trk nerve growth factor (NGF) receptor point mutation affecting interaction with phospholipase C-gamma 1 abolishes NGF-promoted peripherin induction but not neurite outgrowth.

We analyzed the function of Trk nerve growth factor (NGF) receptors containing a point mutation (Tyr-->Phe) in a major autophosphorylation site (Tyr-785). Tyr-785 is required for phospholipase C-gamma 1 to interact with Trk and to become tyrosine-phosphorylated in response to NGF. The altered receptors were transfected into a mutant subline of PC12 rat pheochromocytoma cells (designated PC12nnr5) that, unlike wild-type PC12 cells, lack expression of endogenous Trk and responsiveness to NGF. PC12nnr5 cells permanently transfected with Trk Y785F exhibit NGF-dependent autophosphorylation and normal NGF binding and internalization. Moreover, Trk Y785F mediates NGF-stimulated neurite outgrowth as well as a variety of additional responses including induction of immediate-early and late genes. However, in contrast to cells expressing wild-type Trk, cells expressing Trk Y785F lack NGF-promoted elevation of peripherin intermediate filament mRNA and protein. These observations indicate that phospholipase C-gamma 1 activation or other signaling pathways dependent on Tyr-785 autophosphorylation are selectively required for regulation of peripherin expression by NGF, but not for many other functional NGF responses. This supports the presence of multiple and separable signaling pathways in the NGF mechanism of action.

Amino Acid Sequence↗
PubMed1998

Repeat-induced point mutations in Pad-1, a putative RNA splicing factor from Neurospora crassa, confer dominant lethal effects on ascus development.

We describe the characterization of a gene, Pad-1, from Neurospora crassa which displays sequence characteristics of the RS class of hnRNA-binding proteins (hnRNP) and mRNA splicing factors. This is the first report of the isolation of a putative hnRNP gene from N. crassa. PAD-1 showed 30% identity and 57% similarity to a protein, HCC1, which was isolated using autoantibodies from patients suffering from hepatocellular carcinoma. Both HCC1 and PAD-1 show amino acid sequence similarities to the human splicing factor, U2AF65. Mutations induced in Pad-1 by repeat-induced point (RIP) mutation show dominant effects on ascus and ascospore formation, a novel phenotypic class of RIP mutants. A mutant isolated from the Pad-1 RIP cross displayed a severe vegetative growth defect and dominant effects on ascus development, indicating that Pad-1 is essential for both asexual and sexual development.

Amino Acid Sequence↗
PubMed1984

Mutant hemoglobin stability depends upon location and nature of single point mutation.

The temperature dependence of the rates of heme release from the beta subunits of methemoglobin A and 5 beta mutant methemoglobins has been determined. The rates were largest for two hemoglobins with mutations distal to heme, previously known to be unstable. The other 3 mutants also released heme faster than A. These hemoglobins, with single point mutations at the alpha 1/beta 2 interface, were previously thought to be stable. The low reported yields of the 5 mutant proteins covaries with the relative rates of heme release from the met species.

Heme↗
PubMed1989

Isolation of point mutations that affect the folding of the H chain of human ferritin in E.coli.

We have approached the problem of folding and assembly of the heavy (H) chain of human ferritin by isolating point mutations that affect this process. Apoferritin is an ideal model system to approach the problem of protein folding and assembly into multimeric structures. We have developed a recombinant hybrid molecule that allows us to select for ferritin mutants in which the folding-assembly process is altered or completely impaired. The selection procedure is based on a recombinant protein which consists of a fusion between the H chain of human ferritin and the alpha-peptide of beta-galactosidase. In the wild type situation, the alpha-peptide domain is segregated inside the apoferritin shell upon assembly and is unable to interact with the substrate and perform its enzymic function. We show that by selecting for mutations that restore beta-galactosidase activity we are able to identify ferritin mutations that affect the folding-assembly process. The selective procedure was applied to the analysis of the amino acid side chains that are important for the attainment of the correct conformation of the carboxy-terminal E helix in the 4-fold axis.

Amino Acid Sequence↗
PubMedDate not supplied

Activation of Ki-ras2 gene in human colon and lung carcinomas by two different point mutations.

Kirsten (Ki)-ras cDNA clones were prepared from human lung and colon carcinoma cell lines expressing an activated c-Ki-ras2 gene. DNA sequence analysis and transfection studies indicate that different point mutations at the same codon can activate the gene; that most human c-Ki-ras2 mRNA uses sequences from a fourth coding exon distinct from that of its viral counterpart; and that at least one cell line is functionally homozygous for the activated gene.

Alleles↗
PubMed1999

Point mutations throughout the GLI3 gene cause Greig cephalopolysyndactyly syndrome.

Greig cephalopolysyndactyly syndrome, characterized by craniofacial and limb anomalies (GCPS; MIM 175700), previously has been demonstrated to be associated with translocations as well as point mutations affecting one allele of the zinc finger gene GLI3. In addition to GCPS, Pallister-Hall syndrome (PHS; MIM 146510) and post-axial polydactyly type A (PAP-A; MIM 174200), two other disorders of human development, are caused by GLI3 mutations. In order to gain more insight into the mutational spectrum associated with a single phenotype, we report here the extension of the GLI3 mutation analysis to 24 new GCPS cases. We report the identification of 15 novel mutations present in one of the patient's GLI3 alleles. The mutations map throughout the coding gene regions. The majority are truncating mutations (nine of 15) that engender prematurely terminated protein products mostly but not exclusively N-terminally to or within the central region encoding the DNA-binding domain. Two missense and two splicing mutations mapping within the zinc finger motifs presumably also interfere with DNA binding. The five mutations identified within the protein regions C-terminal to the zinc fingers putatively affect additional functional properties of GLI3. In cell transfection experiments using fusions of the DNA-binding domain of yeast GAL4 to different segments of GLI3, transactivating capacity was assigned to two adjacent independent domains (TA(1)and TA(2)) in the C-terminal third of GLI3. Since these are the only functional domains affected by three C-terminally truncating mutations, we postulate that GCPS may be due either to haploinsufficiency resulting from the complete loss of one gene copy or to functional haploinsufficiency related to compromised properties of this transcription factor such as DNA binding and transactivation.

Animals↗
PubMed1989

A novel method for detecting point mutations or polymorphisms and its application to population screening for carriers of phenylketonuria.

We describe a method termed PCR (polymerase chain reaction) amplification of specific alleles (PASA), a generally applicable technique for detection of point mutations or polymorphisms. The ease and technical simplicity of PASA will make genetic analyses more accessible to the general medical community. In addition, PASA shows promise for population screening because the technique is rapid, highly reproducible, inexpensive, nonisotopic, and amenable to automation. PASA is a modification of PCR that depends on the synthesis of a PCR oligonucleotide primer that precisely matches with one of the alleles but mismatches with the other. When the mismatch occurs near the 3' end of the PCR primer, amplification is inefficient. Therefore, preferential amplification of the perfectly matched allele is obtained. We demonstrate the applicability of PASA by performing carrier detection in the family of a patient with phenylketonuria (PKU) and by screening a population of unrelated subjects for the presence of the two mutations most commonly associated with PKU. Multiple persons were screened simultaneously for the mutant alleles because a mutation could be detected in the presence of at least a 40-fold excess of the normal allele. The two PKU mutations could be detected concurrently by using a mixture of only three PCR primers, an indication that simultaneous screening of multiple mutations can be done even if three or more mutations are closely clustered. In addition to the detection of mutations, PASA can be used to detect polymorphic alleles rapidly and to distinguish pseudogenes or repetitive sequences that differ by as little as one base.

Alleles↗
PubMed2005

Grb7-SH2 domain dimerisation is affected by a single point mutation.

Growth factor receptor bound protein 7 (Grb7) is an adaptor protein that is co-overexpressed and forms a tight complex with the ErbB2 receptor in a number of breast tumours and breast cancer cell lines. The interaction of Grb7 with the ErbB2 receptor is mediated via its Src homology 2 (SH2) domain. Whilst most SH2 domains exist as monomers, recently reported studies have suggested that the Grb7-SH2 domain exists as a homodimer. The self-association properties of the Grb7-SH2 domain were therefore studied using sedimentation equilibrium ultracentrifugation. Analysis of the data demonstrated that the Grb7-SH2 domain is dimeric with a dissociation constant of approximately 11 muM. We also demonstrate, using size-exclusion chromatography, that mutation of phenylalanine 511 to an arginine produces a monomeric form of the Grb7-SH2 domain. This mutation represents the first step in the engineering of a Grb7-SH2 domain with good solution properties for further biophysical and structural investigation.

Arginine↗
PubMed2001

A point mutation in ABC1 gene in a patient with severe premature coronary heart disease and mild clinical phenotype of Tangier disease.

The proband is a 50 year-old woman born from a consanguineous marriage. She has been suffering from angina pectoris since the age of 38 and underwent coronary bypass surgery for three-vessel disease at 48. The presence of low plasma levels of total cholesterol and high density lipoprotein (HDL) cholesterol (2.4 and 0.1 mmol/l) and apo AI (<15 mg/dl), associated with corneal lesions and a mild splenomegaly suggested the diagnosis of Tangier disease. However, none of the other features of Tangier disease, including hepatomegaly, anemia and peripheral neuropathy, were present. The analysis of the dinucleotide microsatellites located in chromosome 9q31 region demonstrated that the proband was homozygous for the alleles of D9S53, D9S1784 and D9S1832. The mother and son of the proband, both with low levels of HDL cholesterol, shared one of the proband's haplotypes, whereas neither of these haplotypes was present in the normolipidemic proband's sister. The sequence of ATP-binding cassette transporter 1 (ABC1-1) cDNA obtained by reverse transcription-PCR (RT-PCR) of total RNA isolated from cultured fibroblasts showed that the proband was homozygous for a C>T transition in exon 13, which caused a tryptophane for arginine substitution (R527W). This mutation was confirmed by direct sequencing of exon 13 amplified from genomic DNA. It can be easily screened, as the nucleotide change introduces a restriction site for the enzyme Afl III. R527W substitution occurs in a highly conserved region of the NH2 cytoplasmic domain of ABC1 protein. R527W co-segregates with the low HDL phenotype in the family and was not found in 200 chromosomes from normolipidemic individuals.

ATP Binding Cassette Transporter 1↗
PubMed1998

Identification of known p53 point mutations by capillary electrophoresis using unique mobility profiles in a blinded study.

This study is part of an ongoing project at the National Institute of Standards and Technology (NIST) that generates a panel of DNA clones containing the most common mutations found in the human p53 tumor suppressor gene. This panel will be made available as a reference source for evaluation and testing for p53 mutations. Single strand conformation polymorphism (SSCP) analysis has found widespread acceptance as a tool for simply and rapidly screening for mutations, albeit with a detection rate that can be below 100%. We have begun to analyze mutations found in exon 7 of the p53 gene by SSCP using laser induced fluorescence capillary electrophoresis (LIF-CE). PCR fragments, containing single point mutations, were amplified from genomic DNA isolated from cell lines using primers labeled with two different fluorophores. This dual labeling approach allowed better traceability of mobility shifts as a function of the experimental conditions. While analyzing the clones H596, Colo320, Namalwa and wild type (reference samples) at different temperatures, ranging from 25 to 45 degrees C, it was observed that each mutation responded in a unique way to changes in temperature both in magnitude and direction of shifts relative to the wild type sample. In a blinded study, ten p53 exon 7 samples were matched automatically, using ABI PRISM Genotyper software, against the four reference samples. From these 10 samples, six were correctly identified as containing one of the reference mutations, two corresponded to wild type, and two were correctly identified as non-reference mutations. This approach should prove helpful in the rapid screening of target sequences that are known to bear a limited number of mutations.

Automation↗
PubMed2003

Point mutations induced by foscarnet (PFA) in the human cytomegalovirus DNA polymerase.

BACKGROUND: In vitro selection of viruses with decreased drug susceptibility is a useful tool for mapping drug resistance-associated alterations, evaluating cross-resistance profiles, and elucidating molecular mechanisms of antiviral activity. OBJECTIVES: To provide data on mechanisms of selective drug action and features of drug resistance that may be clinically important. STUDY DESIGN: Foscarnet (PFA) and ganciclovir (GCV) were used to induce mutants of the human cytomegalovirus (HCMV) Towne strain. RESULTS: Three new mutations, selected in the presence of PFA, were identified with single base substitutions resulting in T419M, Q578H, and L773V in conserved regions of the HCMV DNA polymerase. None of these mutations have been reported previously. These mutations conferred resistance to PFA but did not change the susceptibility to GCV. A mutant was selected in the presence of GCV. This GCV-selected mutant had no mutation in the UL54 but had an amino acid alteration at codon M460V of UL97, which conferred resistance to GCV. All the mutants had the same growth phenotype as the parental laboratory strain Towne. CONCLUSIONS: We have determined three novel alterations in HCMV DNA polymerase inducing reduced susceptibility to PFA. None of these alterations changed the growth phenotype of the parental virus.

Amino Acid Substitution↗
PubMed2004

A novel point mutation of the RET protooncogene involving the second intracellular tyrosine kinase domain in a family with medullary thyroid carcinoma.

Hereditary medullary thyroid carcinoma, a tumor that arises from the parafollicular cells of the thyroid gland, occurs in isolation (as in familial medullary thyroid carcinoma), in association with hyperparathyroidism and pheochromocytoma (as in multiple endocrine neoplasia type 2A), or in association with pheochromocytoma, marfanoid habitus, and mucosal neuromas (as in multiple endocrine neoplasia type 2B). These genetic syndromes are associated with germline-activating mutations of the RET protooncogene, a cell surface tyrosine kinase receptor, which is believed to modulate specific intracellular signaling pathways involved in the regulation of C cell proliferation and apoptosis. RET-activating mutations involve two important functional areas of the receptor: the cysteine-rich extracellular domain and the intracellular tyrosine kinase domain. Multiple endocrine neoplasia type 2A and familial medullary thyroid carcinoma are more commonly associated with mutations in the cysteine-rich extracellular domain, whereas multiple endocrine neoplasia type 2B is exclusively associated with mutations involving the second intracellular tyrosine kinase domain. Here, we describe a novel missense mutation of the RET protooncogene that substitutes arginine for proline at codon 912 of the intracellular tyrosine kinase domain in a family with medullary thyroid carcinoma.

Adolescent↗