Hls
Mostrando 37-48 de 59 artigos, teses e dissertações.
-
37. Requirement for d(GATC) sequences in Escherichia coli mutHLS mismatch correction.
The involvement of d(GATC) sequences in Escherichia coli DNA mismatch correction was ascertained by analyzing in vitro repair efficiencies of a series of related, covalently closed circular DNA heteroduplexes that contained from zero to four d(GATC) sites. A heteroduplex with four d(GATC) sites was repaired with high efficiency by extracts of E. coli, wherea
-
38. The DNA binding properties of the MutL protein isolated from Escherichia coli.
The mutL gene of Escherichia coli, which is involved in the repair of mispaired and unpaired nucleotides in DNA, has been independently cloned and the gene product purified. In addition to restoring methyl-directed DNA repair in extracts prepared from mutL strains, the purified MutL protein binds to both double and single stranded DNA. The affinity constant
-
39. Mutation detection with MutH, MutL, and MutS mismatch repair proteins.
Escherichia coli methyl-directed mismatch repair is initiated by MutS-, MutL-, and ATP-dependent activation of MutH endonuclease, which cleaves at d(GATC) sites in the vicinity of a mismatch. This reaction provides an efficient method for detection of mismatches in heteroduplexes produced by hybridization of genetically distinct sequences after PCR amplifica
-
40. Proofreading-defective DNA polymerase II increases adaptive mutation in Escherichia coli.
The role of Escherichia coli DNA polymerase (Pol) II in producing or avoiding mutations was investigated by replacing the chromosomal Pol II gene (polB+) by a gene encoding an exonuclease-deficient mutant Pol II (polBex1). The polBex1 allele increased adaptive mutations on an episome in nondividing cells under lactose selection. The presence of a Pol III ant
-
41. Statistical evaluation and biological interpretation of non-random abundance in the E. coli K-12 genome of tetra- and pentanucleotide sequences related to VSP DNA mismatch repair.
The abundance of all tetra- and pentanucleotide sequences is calculated for a set of DNA sequence data comprising 767,393 nucleotides of the E. coli K-12 genome. Observed frequencies are compared to those expected from a Markov chain prediction algorithm. Systematic and extreme non-random representations are found for special sets of sequences. These are int
-
42. Strand-specific mismatch correction in nuclear extracts of human and Drosophila melanogaster cell lines.
Nuclear extracts derived from HeLa and Drosophila melanogaster KC cell lines have been found to correct single base-base mispairs within open circular DNA heteroduplexes containing a strand-specific, site-specific incision located 808 base pairs from the mismatch. Correction in both extract systems is strand specific, being highly biased to the incised DNA s
-
43. Efficient gene targeted random mutagenesis in genetically stable Escherichia coli strains
We describe a method to generate in vivo collections of mutants orders of magnitude larger than previously possible. The method favors accumulation of mutations in the target gene, rather than in the host chromosome. This is achieved by propagating the target gene on a plasmid, in Escherichia coli cells, within the region preferentially replicated by DNA pol
Oxford University Press.
-
44. Heteroduplexes in mixed-template amplifications: formation, consequence and elimination by ‘reconditioning PCR’
Although it has been recognized that PCR amplification of mixed templates may generate sequence artifacts, the mechanisms of their formation, frequency and potential elimination have not been fully elucidated. Here evidence is presented for heteroduplexes as a major source of artifacts in mixed-template PCR. Nearly equal proportions of homoduplexes and heter
Oxford University Press.
-
45. Identification of Hodgkin and Reed-Sternberg cell-specific genes by gene expression profiling
Hodgkin lymphoma (HL) is a malignancy of unknown pathogenesis. The malignant Hodgkin and Reed/Sternberg (HRS) cells derive from germinal center B cells (or rarely, T cells) but have a heterogeneous and largely uncharacterized phenotype. Using microarrays, we compared the gene expression profile of four HL cell lines with profiles of the main B cell subsets a
American Society for Clinical Investigation.
-
46. The extreme mutator effect of Escherichia coli mutD5 results from saturation of mismatch repair by excessive DNA replication errors.
Escherichia coli mutator mutD5 is the most potent mutator known. The mutD5 mutation resides in the dnaQ gene encoding the proofreading exonuclease of DNA polymerase III holoenzyme. It has recently been shown that the extreme mutability of this strain results, in addition to a proofreading defect, from a defect in mutH, L, S-encoded postreplicational DNA mism
-
47. Pathway correcting DNA replication errors in Saccharomyces cerevisiae.
Mutation of predicted 3'-->5' exonuclease active site residues of Saccharomyces cerevisiae POL3 DNA polymerase (delta) or deletion of the PMS1 mismatch repair gene lead to relative (to wild type) spontaneous mutation rates of approximately 130 and 41, respectively, measured at a URA3 reporter gene inserted near to a defined replication origin. The POL3 exonu
-
48. Mechanisms of mutagenesis in the Escherichia coli mutator mutD5: role of DNA mismatch repair.
To investigate the mechanisms of spontaneous mutation in the Escherichia coli mutD5 mutator strain, 502 mutations generated in this strain in the N-terminal part of the lacI gene were sequenced (i-d mutations). Since the mutator strength of this strain depends on the medium in which it grows, mutations were analyzed in both minimal medium (moderate mutator a