The yeast rad18 mutator specifically increases G.C----T.A transversions without reducing correction of G-A or C-T mismatches to G.C pairs

1991 ◽  
Vol 11 (1) ◽  
pp. 218-225
Author(s):  
B A Kunz ◽  
X L Kang ◽  
L Kohalmi
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dna Synthesis ◽  
Dna Sequence ◽  
Base Pair ◽  
Mutation Frequency ◽  
Wild Type ◽  
Sequence Context ◽  
Single Base ◽  
Mutator Effect ◽  
Single Base Pair

Inactivation of the Saccharomyces cerevisiae RAD18 gene confers a mutator phenotype. To determine the specificity of this effect, a collection of 212 spontaneous SUP4-o mutants arising in a rad18 strain was characterized by DNA sequencing. Comparison of the resulting mutational spectrum with that for an isogenic wild-type (RAD18) strain revealed that the rad18 mutator specifically enhanced the frequency of single base pair substitutions. Further analysis indicated that an increase in the frequency of G.C----T.A transversions accounted for the elevated SUP4-o mutation frequency. Thus, rad18 is the first eucaryotic mutator found to generate only a particular base pair substitution. The majority of G.C pairs that were not mutated in the rad18 background were at sites where G.C----T.A events can be detected in SUP4-o, suggesting that DNA sequence context influences the rad18 mutator effect. Transformation of heteroduplex plasmid DNAs into the two strains demonstrated that the rad18 mutator did not reduce the efficiency of correcting G-A or C-T mismatches to G.C pairs or preferentially correct the mismatches to A.T pairs. We propose that the RAD18 gene product might contribute to the fidelity of DNA replication in S. cerevisiae by involvement in a process that serves to limit the formation of G-A and C-T mismatches at template guanine and cytosine sites during DNA synthesis.

scholarly journals The yeast rad18 mutator specifically increases G.C----T.A transversions without reducing correction of G-A or C-T mismatches to G.C pairs.

1991 ◽  
Vol 11 (1) ◽  
pp. 218-225 ◽  
Author(s):  
B A Kunz ◽  
X L Kang ◽  
L Kohalmi
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dna Synthesis ◽  
Dna Sequence ◽  
Base Pair ◽  
Mutation Frequency ◽  
Wild Type ◽  
Sequence Context ◽  
Single Base ◽  
Mutator Effect ◽  
Single Base Pair

Inactivation of the Saccharomyces cerevisiae RAD18 gene confers a mutator phenotype. To determine the specificity of this effect, a collection of 212 spontaneous SUP4-o mutants arising in a rad18 strain was characterized by DNA sequencing. Comparison of the resulting mutational spectrum with that for an isogenic wild-type (RAD18) strain revealed that the rad18 mutator specifically enhanced the frequency of single base pair substitutions. Further analysis indicated that an increase in the frequency of G.C----T.A transversions accounted for the elevated SUP4-o mutation frequency. Thus, rad18 is the first eucaryotic mutator found to generate only a particular base pair substitution. The majority of G.C pairs that were not mutated in the rad18 background were at sites where G.C----T.A events can be detected in SUP4-o, suggesting that DNA sequence context influences the rad18 mutator effect. Transformation of heteroduplex plasmid DNAs into the two strains demonstrated that the rad18 mutator did not reduce the efficiency of correcting G-A or C-T mismatches to G.C pairs or preferentially correct the mismatches to A.T pairs. We propose that the RAD18 gene product might contribute to the fidelity of DNA replication in S. cerevisiae by involvement in a process that serves to limit the formation of G-A and C-T mismatches at template guanine and cytosine sites during DNA synthesis.

scholarly journals Disruption of the RAD52 gene alters the spectrum of spontaneous SUP4-o mutations in Saccharomyces cerevisiae.

Genetics ◽  
1989 ◽  
Vol 122 (3) ◽  
pp. 535-542 ◽  
Author(s):  
B A Kunz ◽  
M G Peters ◽  
S E Kohalmi ◽  
J D Armstrong ◽  
M Glattke ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Base Pair ◽  
Type Strain ◽  
Wild Type Strain ◽  
Wild Type ◽  
Yeast Saccharomyces Cerevisiae ◽  
Mutator Phenotype ◽  
In The Wild ◽  
Single Base Pair ◽  
Almost All

Abstract Defects in the RAD52 gene of the yeast Saccharomyces cerevisiae confer a mutator phenotype. To characterize this effect in detail, a collection of 238 spontaneous SUP4-o mutations arising in a strain having a disrupted RAD52 gene was analyzed by DNA sequencing. The resulting mutational spectrum was compared to that derived from an examination of 222 spontaneous mutations selected in a nearisogenic wild-type (RAD52) strain. This comparison revealed that the mutator phenotype was associated with an increase in the frequency of base-pair substitutions. All possible types of substitution were detected but there was a reduction in the relative fraction of A.T----G.C transitions and an increase in the proportion of G.C----C.G transversions. These changes were sufficient to cause a twofold greater preference for substitutions at G.C sites in the rad52 strain despite a decrease in the fraction of G.C----T.A transversions. There were also considerable differences between the distributions of substitutions within the SUP4-o gene. Base-pair changes occurred at fewer sites in the rad52 strain but the mutated sites included several that were not detected in the RAD52 background. Only two of the four sites that were mutated most frequently in the rad52 strain were also prominent in the wild-type strain and mutation frequencies at almost all sites common to both strains were greater for the rad52 derivative. Although single base-pair deletions occurred in the two strains with similar frequencies, several classes of mutation that were recovered in the wild-type background including multiple base-pair deletions, insertions of the yeast transposable element Ty, and more complex changes, were not detected in the rad52 strain.(ABSTRACT TRUNCATED AT 250 WORDS)

Aberrant Somatic Hypermutation in Primary Mediastinal Large B-Cell Lymphoma.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 2268-2268 ◽  
Author(s):  
Davide Rossi ◽  
Michaela Cerri ◽  
Daniela Capello ◽  
Clara Deambrogi ◽  
Eva Berra ◽  
...  
Keyword(s):  
B Cell ◽  
Base Pair ◽  
Mutation Frequency ◽  
Cell Lymphoma ◽  
Somatic Hypermutation ◽  
B Cell Lymphoma ◽  
Single Base ◽  
Large B Cell Lymphoma ◽  
Single Base Pair ◽  
Large B Cell

Abstract Primary mediastinal large B-cell lymphoma (PMLBCL) is recognised as a subtype of diffuse large B-cell lymphoma (DLBCL) arising in the mediastinum. With respect to DLBCL, PMLBCL displays specific clinical, molecular and morphological features suggesting that PMLBCL may represent a distinct clinico-pathologic entity. Aberrant somatic hypermutation (SHM) of PIM-1, PAX-5, RhoH/TTF and c-MYC has been advocated as a molecular feature distinctive of DLBCL. To investigate wether the same mechanism is associated with PMLBCL, we performed mutational analysis of PIM-1, PAX-5, RhoH/TTF and c-MYC in a panel of 19 PMLBCL. For comparison, 19 DLBCL were also analysed. For each gene, a region previously shown to contain >90% of mutations was analysed by PCR amplification and DNA direct sequencing. Overall, the prevalence of mutated cases was similar among DLBCL and PMLBCL. Mutations targeting at least one of the 4 genes were found in 14/19 (73.6%) PMLBCL and 13/19 (68.4%) DLBCL, while mutations in more than one gene were found in 7/19 (36.8%) PMLBCL and 9/19 (47.3%) DLBCL. Among the four genes, the prevalence of mutation and the mutation frequency was superimposable between PMLBCL and DLBCL. In fact, PAX-5 was mutated in 9/19 (47.3%) PMLBCL with a mean mutation frequency of 0.20 x 10−2/bp and in 7/19 (36.8%) DLBCL with a mean mutation frequency of 0.18 x 10−2/bp; RhoH/TTF was mutated in 6/19 (31.5%) PMLBCL with a mean mutation frequency of 0.08 x 10−2/bp and in 8/19 (42.1%) DLBCL with a mean mutation frequency of 0.27 x 10−2/bp; PIM-1 was mutated in 3/19 (15.7%) PMLBCL with a mean mutation frequency of 0.09 x 10−2/bp and in 7/19 (36.8%) DLBCL with a mean mutation frequency of 0.11 x 10−2/bp; c-MYC was mutated in 6/19 (31.5%) PMLBCL with a mean mutation frequency of 0.23 x 10−2/bp and in 5/19 (26.3%) DLBCL with a mean mutation frequency of 0.11 x 10−2. The mutation pattern was also similar between PMLBCL and DLBCL and was consistent with the SHM process. A total of 74 mutational events were detected in PMLBCL. The majority of mutations were represented by single base-pair substitution (n=66), whereas only 8 deletions of a short DNA stretch were observed. Of the 66 single base-pair substitutions, 41 were transitions and 25 were transversions, with a transition/transversion ratio of 1.64 and a G+C/A+T ratio of 3.6. Eleven out of 66 (16.6%) single base-pair substitutions felt within RGYW/WRCY motifs. Among DLBCL a total of 87 mutational events were detected. Mutations were preferentially represented by single base-pair substitutions (n=81), whereas only 4 deletions and 2 insertions of a short DNA stretch were observed. Of the 81 single base-pair substitutions, 42 were transitions and 39 were transversions, with a transition/transversion ratio of 1.07 and a G+C/A+T ratio of 1.89. Twenty six out of 81 (32.1%) single base-pair substitutions felt within RGYW/WRCY motifs. The implication of our results are twofold. First, aberrant SHM is involved in the pathogenesis of PMLBCL. Second, our results indicate that aberrant SHM targets both PMLBCL and DLBCL with similar prevalence, distribution and mutation pattern. Since aberrant SHM has been advocated as a molecular marker of DLBCL, our results corroborate the notion that PMLBCL represent a subtype of DLBCL rather than a distinct clinico-pathologic entity.

Sequence Context and Thermodynamic Stability of a Single Base Pair Mismatch in Short Deoxyoligonucleotide Duplexes

2001 ◽  
Vol 123 (47) ◽  
pp. 11811-11812 ◽  
Author(s):  
Timothy S. Hall ◽  
Petr Pancoska ◽  
Peter V. Riccelli ◽  
Kathleen Mandell ◽  
Albert S. Benight
Keyword(s):  
Thermodynamic Stability ◽  
Base Pair ◽  
Sequence Context ◽  
Single Base ◽  
Base Pair Mismatch ◽  
Single Base Pair

scholarly journals Point mutations implicate repeated sequences as essential elements of the CYC7 negative upstream site in Saccharomyces cerevisiae.

1985 ◽  
Vol 5 (11) ◽  
pp. 2951-2958 ◽  
Author(s):  
C F Wright ◽  
R S Zitomer
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dna Sequences ◽  
Base Pair ◽  
Point Mutations ◽  
Regulatory Elements ◽  
Upstream Site ◽  
Single Base ◽  
Negative Element ◽  
Single Base Pair ◽  
Single Base Pair Change

The transcription of the CYC7 gene of Saccharomyces cerevisiae, encoding the iso-2-cytochrome c protein, is controlled by two upstream regulatory elements, a positive element and a negative element. The nature of the DNA sequences in the negative element were investigated in a two-part approach. The first involved the construction of a CYC7-galK fusion gene which placed the coding sequence of the Escherichia coli galactokinase gene under the regulation of the CYC7 upstream sequences. This fusion allowed the quantitation by galactokinase enzyme assays of the effects on gene expression of a variety of previously isolated deletion mutations within the negative site. The results suggested that the negative site contained three related sequences. This hypothesis was tested in the second part of these studies, the selection of point mutations within the region of the negative site which led to increased CYC7 expression. Point mutations were introduced by a technique which induced mutations within a localized region at high efficiency. All but one of the mutations involved more than a single base-pair change. The mutations followed the pattern that multiple base-pair changes occurred in one repeat or single base-pair changes occurred in two repeats, with the exception of one mutant, which had a single base-pair change in one repeat. This pattern of mutations and the base pairs that were altered strongly supported the hypothesis that the repeats are integral elements of the negative site.

scholarly journals A single base pair dominates over the novel identity of an Escherichia coli tyrosine tRNA in Saccharomyces cerevisiae.

1991 ◽  
Vol 11 (5) ◽  
pp. 2744-2751 ◽  
Author(s):  
V Trézéguet ◽  
H Edwards ◽  
P Schimmel
Keyword(s):  
Escherichia Coli ◽  
Saccharomyces Cerevisiae ◽  
Base Pair ◽  
Major Determinant ◽  
The Novel ◽  
Single Base ◽  
E Coli ◽  
Single Base Pair

The Escherichia coli su+3 tyrosine tRNA was shown recently to be a leucine-specific tRNA in Saccharomyces cerevisiae. This finding raises the possibility that some determinants for tRNA identity in E. coli may be different in S. cerevisiae. To investigate whether the fungal system is sensitive to the major determinant for alanine acceptance in E. coli, a single G3 . U70 base pair was introduced into the acceptor helix of the su+3 tyrosine tRNA. This substitution converts the identity of the E. coli suppressor in S. cerevisiae from leucine to alanine. Thus, as in E. coli, G3 . U70 is a strong determinant for alanine acceptance that can dominate over other features in a tRNA that might be recognized by alternative charging enzymes.

scholarly journals Mechanisms of activation of the cryptic cel operon of Escherichia coli K12.

Genetics ◽  
1990 ◽  
Vol 124 (3) ◽  
pp. 473-482 ◽  
Author(s):  
L L Parker ◽  
B G Hall
Keyword(s):  
Escherichia Coli ◽  
Base Pair ◽  
Point Mutations ◽  
Insertion Sequences ◽  
Wild Type ◽  
Single Base ◽  
Escherichia Coli K12 ◽  
In The Wild ◽  
Single Base Pair ◽  
Strain Dependent

Abstract The cel (cellobiose utilization) operon of Escherichia coli K12 is not expressed in the wild-type organism. However, mutants that can express the operon and thereby utilize the beta-glucoside sugars cellobiose, arbutin and salicin are easily isolated. Two kinds of mutations are capable of activating the operon. The first involves mutations that allow the repressor to recognize the substrates cellobiose, arbutin and salicin as inducers. We have identified the sequence changes in five different active alleles and found those differences to be single base pair changes at one of two lysine codons in the repressor gene. The second kind of mutation involves the integration of the insertion sequences IS1, IS2 or IS5 into a 108-bp region 72-180 bp upstream of the start of transcription. Integration occurs at several different sites and in different orientations. Transcription of the cel operon begins at the same base pair in all mutants examined. Of 44 independent cel+ mutants, 27 were activated by point mutations and 17 were activated by insertion sequences. The preferred mechanism of activation appears to be strain dependent, since one of the parents yielded 94% insertionally activated alleles, while another yielded 100% point mutation activated alleles.

Point mutations implicate repeated sequences as essential elements of the CYC7 negative upstream site in Saccharomyces cerevisiae

1985 ◽  
Vol 5 (11) ◽  
pp. 2951-2958
Author(s):  
C F Wright ◽  
R S Zitomer
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dna Sequences ◽  
Base Pair ◽  
Point Mutations ◽  
Regulatory Elements ◽  
Upstream Site ◽  
Single Base ◽  
Negative Element ◽  
Single Base Pair ◽  
Single Base Pair Change

The transcription of the CYC7 gene of Saccharomyces cerevisiae, encoding the iso-2-cytochrome c protein, is controlled by two upstream regulatory elements, a positive element and a negative element. The nature of the DNA sequences in the negative element were investigated in a two-part approach. The first involved the construction of a CYC7-galK fusion gene which placed the coding sequence of the Escherichia coli galactokinase gene under the regulation of the CYC7 upstream sequences. This fusion allowed the quantitation by galactokinase enzyme assays of the effects on gene expression of a variety of previously isolated deletion mutations within the negative site. The results suggested that the negative site contained three related sequences. This hypothesis was tested in the second part of these studies, the selection of point mutations within the region of the negative site which led to increased CYC7 expression. Point mutations were introduced by a technique which induced mutations within a localized region at high efficiency. All but one of the mutations involved more than a single base-pair change. The mutations followed the pattern that multiple base-pair changes occurred in one repeat or single base-pair changes occurred in two repeats, with the exception of one mutant, which had a single base-pair change in one repeat. This pattern of mutations and the base pairs that were altered strongly supported the hypothesis that the repeats are integral elements of the negative site.

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