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.

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 Mutations in the csgD Promoter Associated with Variations in Curli Expression in Certain Strains ofEscherichia coli O157:H7

2001 ◽  
Vol 67 (5) ◽  
pp. 2367-2370 ◽  
Author(s):  
Gaylen A. Uhlich ◽  
James E. Keen ◽  
Robert O. Elder
Keyword(s):  
Escherichia Coli ◽  
Base Pair ◽  
Congo Red ◽  
Substrate Utilization ◽  
Ofescherichia Coli ◽  
Single Base ◽  
Curli Fiber ◽  
Single Base Pair ◽  
Red Dye ◽  
Promoter Mutations

ABSTRACT Single-base-pair csgD promoter mutations in human outbreak Escherichia coli O157:H7 strains ATCC 43894 and ATCC 43895 coincided with differential Congo red dye binding from curli fiber expression. Red phenotypecsgD::lacZ promoter fusions had fourfold-greater expression than white promoter fusions. Cloning the red variant csgDEFG operon into white variants induced the red phenotype. Substrate utilization differed between red and white variants.

scholarly journals RNA minihelices as model substrates for ATP/CTP:tRNA nucleotidyltransferase

1997 ◽  
Vol 327 (3) ◽  
pp. 847-851 ◽  
Author(s):  
Zengji LI ◽  
Yue SUN ◽  
L. David THURLOW
Keyword(s):  
Escherichia Coli ◽  
Saccharomyces Cerevisiae ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Single Base ◽  
Three Dimensional Structure ◽  
E Coli ◽  
Base Identity

Twenty-one RNA minihelices, resembling the coaxially stacked acceptor- /T-stems and T-loop found along the top of a tRNA's three-dimensional structure, were synthesized and used as substrates for ATP/CTP:tRNA nucleotidyltransferases from Escherichia coli and Saccharomyces cerevisiae. The sequence of nucleotides in the loop varied at positions corresponding to residues 56, 57 and 58 in the T-loop of a tRNA. All minihelices were substrates for both enzymes, and the identity of bases in the loop affected the interaction. In general, RNAs with purines in the loop were better substrates than those with pyrimidines, although no single base identity absolutely determined the effectiveness of the RNA as substrate. RNAs lacking bases near the 5ʹ-end were good substrates for the E. coli enzyme, but were poor substrates for that from yeast. The apparent Km values for selected minihelices were 2-3 times that for natural tRNA, and values for apparent Vmax were lowered 5-10-fold.

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.

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 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.

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.

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