Isolation and analysis of a novel class of suppressor of Ty insertion mutations in Saccharomyces cerevisiae.

Genetics ◽  
1988 ◽  
Vol 118 (2) ◽  
pp. 203-212
Author(s):  
J S Fassler ◽  
F Winston
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Gene Transcription ◽  
Transcriptional Analysis ◽  
Insertion Mutation ◽  
Gene Products ◽  
Adjacent Gene ◽  
Cellular Functions ◽  
Ty Elements ◽  
Insertion Mutations

Abstract Using a new scheme for the isolation of suppressor of Ty insertion mutations (spt mutations) in yeast, we have identified six new SPT genes. Mutations in two of these genes, SPT13 and SPT14, exhibit a novel suppression pattern: suppression of complete Ty insertion mutations, but not of solo delta insertion mutations. Transcriptional analysis shows that spt13- and spt14-mediated suppression of Ty insertion mutations is the result of an elevation in the levels of adjacent gene transcription. In spite of the failure of these mutations to suppress solo delta insertion mutations, they do cause changes in transcription of at least one solo delta insertion mutation. In addition, spt13 and spt14 mutations are epistatic to mutations in certain other SPT genes that do suppress solo delta insertion mutations. These results suggest that the SPT13 and SPT14 gene products may act via sequences in both the delta and epsilon regions of Ty elements. Finally, mutations in SPT13 cause sporulation and mating defects and SPT14 is essential for growth, suggesting that these two genes have important roles in general cellular functions.

scholarly journals The SNF2, SNF5 and SNF6 genes are required for Ty transcription in Saccharomyces cerevisiae.

Genetics ◽  
1991 ◽  
Vol 128 (1) ◽  
pp. 69-77 ◽  
Author(s):  
A M Happel ◽  
M S Swanson ◽  
F Winston
Keyword(s):  
Gene Expression ◽  
Saccharomyces Cerevisiae ◽  
Gene Products ◽  
Adjacent Gene ◽  
Ty Elements ◽  
Distinct Mechanism ◽  
Insertion Mutations

Abstract The Saccharomyces cerevisiae SNF2, SNF5 and SNF6 genes were initially identified as genes required for expression of SUC2 and other glucose repressible genes. The Suc- defect in all three of these classes of mutants is suppressed by mutations in the SPT6 gene. Since mutations in SPT6 had also been identified as suppressors of Ty and solo delta insertion mutations at the HIS4 and LYS2 loci, we have examined Ty transcription in snf2, snf5 and snf6 mutants and have found that Ty transcription is abolished or greatly reduced. The snf2, snf5 and snf6 defect for Ty transcription, like the defect for SUC2 transcription, is suppressed by spt6 mutations. In contrast to other mutations that abolish or greatly reduce Ty transcription (in the SPT3, SPT7 and SPT8 genes), mutations in these SNF genes do not cause suppression of insertion mutations. This result suggests that the SNF2, SNF5 and SNF6 gene products act by a distinct mechanism from the SPT3, SPT7 and SPT8 gene products to promote transcription of Ty elements. This result also suggests that a reduction of Ty transcription is not always sufficient for activation of adjacent gene expression.

scholarly journals MUTATIONS AFFECTING TY-MEDIATED EXPRESSION OF THE HIS4 GENE OF SACCHAROMYCES CEREVISIAE

Genetics ◽  
1984 ◽  
Vol 107 (2) ◽  
pp. 179-197 ◽  
Author(s):  
Fred Winston ◽  
Deborah T Chaleff ◽  
Barbara Valent ◽  
Gerald R Fink
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dna Repair ◽  
Noncoding Region ◽  
Cellular Functions ◽  
Insertion Mutations ◽  
His4 Gene

ABSTRACT We have identified mutations in seven unlinked genes (SPT genes) that affect the phenotypes of Ty and δ insertion mutations in the 5′ noncoding region of the HIS4 gene of S. cerevisiae. Spt mutants were selected for suppression of his4-912δ, a solo δ derivative of Ty912. Other Ty and δ insertions at HIS4 are suppressed by mutations in some but not all of the SPT genes. Only spt4 suppresses a non-Ty insertion at HIS4. In addition to their effects on Ty and δ insertions, mutations in several SPT genes show defects in general cellular functions—mating. DNA repair and growth.

scholarly journals Transcriptional analysis of Ty1 deletion and inversion derivatives at CYC7

1986 ◽  
Vol 6 (10) ◽  
pp. 3299-3311
Author(s):  
M Company ◽  
B Errede
Keyword(s):  
Cytochrome C ◽  
Transcriptional Activation ◽  
Fold Increase ◽  
Transcriptional Analysis ◽  
Insertion Mutation ◽  
Adjacent Gene ◽  
Coding Region ◽  
Deletion Derivative ◽  
And Inversion ◽  
Derivatives Of

One class of Ty insertion mutation in Saccharomyces cerevisiae activates expression of adjacent structural genes. The CYC7-H2 mutation, in which a Ty1 element is inserted 5' to the iso-2-cytochrome c coding region of CYC7, causes a 20-fold increase in CYC7 expression. Deletion analysis of CYC7-H2 has shown that distal regions of the Ty1 element are not essential for the transcriptional activation at CYC7. In this report, we have analyzed Ty1 and CYC7 RNA from two CYC7-H2 deletion derivative genes to determine whether a direct correlation exists between transcription of Ty1 and transcription of the adjacent gene. Assuming that all Ty1 elements in the genome are transcribed equally, amounts of CYC7-H2 deletion derivative Ty1 RNA were found to be at least fivefold lower than the amount estimated for the average Ty1 element. These same Ty1 deletion derivatives caused a 20-fold increase in adjacent CYC7 expression. This finding suggests that the mechanism by which Ty1 activates adjacent gene expression does not require normal levels of Ty1 transcription. Two inversion derivatives of the CYC7-H2 Ty1 have also been analyzed. These derivatives did not produce any iso-2-cytochrome c or any normal CYC7 mRNA. Instead they were found to produce a Tyl-CYC7 fusion RNA. Consistent with our findings on CYC7-H2 Ty1 transcription, the amount of the fusion RNA was very low. In addition, the Ty1 inversion derivatives produced a new RNA that mapped to sequences upstream from the inverted Ty1 segment. Similar to Ty1 insertions that activate transcription, the new RNA was found to be transcribed away from Ty1.

scholarly journals Extragenic suppressors of mar2(sir3) mutations in Saccharomyces cerevisiae.

Genetics ◽  
1990 ◽  
Vol 125 (2) ◽  
pp. 321-331
Author(s):  
C I Lin ◽  
G P Livi ◽  
J M Ivy ◽  
A J Klar
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Gene Transcription ◽  
Transcriptional Control ◽  
Gene Products ◽  
Transcript Analysis ◽  
Mating Type Genes ◽  
Regulatory Loci ◽  
Extragenic Suppressors ◽  
Simultaneous Expression ◽  
New Alleles

Abstract The silent mating-type genes (HML and HMR) of Saccharomyces cerevisiae are kept under negative transcriptional control by four trans-acting MAR (or SIR) loci. We have isolated extragenic suppressors of the mar2-1 mutation which, based on genetic complementation tests, define two additional loci involved in regulating the expression of HML and HMR. A strain with the genotype HMLa MAT alpha HMRa mar2-1 is sterile due to the simultaneous expression of a and alpha information. Two mutants exhibiting an alpha phenotype (which may result from the restoration of MAR/SIR repression) were isolated and genetically characterized. The mutations in these strains: (1) are recessive, (2) are capable of suppressing a mar2-deletion mutation, (3) are unlinked to MAT, (4) complement one another as well as the previously identified sum1-1 mutation, and (5) are not new alleles of the known MAR/SIR loci. We designate these new regulatory loci SUM2 and SUM3 (suppressor of mar). Unlike the sum1-1 mutation, suppression by sum2-1 and sum3-1 is mar2-locus specific. Both sum2-1 and sum3-1 affect the expression of a information at the HM loci. Transcript analysis shows a significant reduction in HMLa and HMRa gene transcription in mar2-1 sum2-1 and mar2-1 sum3-1 cells. Furthermore, we have found genetic evidence to suggest that mar2-1 sum2-1 cells exhibit only partial expression of silent alpha information. We conclude that the SUM2 and SUM3 gene products are required for expression of the HM loci and act downstream of the MAR2 (SIR3) gene function. Possible mechanisms for the action of the SUM gene products are discussed.

scholarly journals Transcriptional analysis of Ty1 deletion and inversion derivatives at CYC7.

1986 ◽  
Vol 6 (10) ◽  
pp. 3299-3311
Author(s):  
M Company ◽  
B Errede
Keyword(s):  
Cytochrome C ◽  
Transcriptional Activation ◽  
Fold Increase ◽  
Transcriptional Analysis ◽  
Insertion Mutation ◽  
Adjacent Gene ◽  
Coding Region ◽  
Deletion Derivative ◽  
And Inversion ◽  
Derivatives Of

One class of Ty insertion mutation in Saccharomyces cerevisiae activates expression of adjacent structural genes. The CYC7-H2 mutation, in which a Ty1 element is inserted 5' to the iso-2-cytochrome c coding region of CYC7, causes a 20-fold increase in CYC7 expression. Deletion analysis of CYC7-H2 has shown that distal regions of the Ty1 element are not essential for the transcriptional activation at CYC7. In this report, we have analyzed Ty1 and CYC7 RNA from two CYC7-H2 deletion derivative genes to determine whether a direct correlation exists between transcription of Ty1 and transcription of the adjacent gene. Assuming that all Ty1 elements in the genome are transcribed equally, amounts of CYC7-H2 deletion derivative Ty1 RNA were found to be at least fivefold lower than the amount estimated for the average Ty1 element. These same Ty1 deletion derivatives caused a 20-fold increase in adjacent CYC7 expression. This finding suggests that the mechanism by which Ty1 activates adjacent gene expression does not require normal levels of Ty1 transcription. Two inversion derivatives of the CYC7-H2 Ty1 have also been analyzed. These derivatives did not produce any iso-2-cytochrome c or any normal CYC7 mRNA. Instead they were found to produce a Tyl-CYC7 fusion RNA. Consistent with our findings on CYC7-H2 Ty1 transcription, the amount of the fusion RNA was very low. In addition, the Ty1 inversion derivatives produced a new RNA that mapped to sequences upstream from the inverted Ty1 segment. Similar to Ty1 insertions that activate transcription, the new RNA was found to be transcribed away from Ty1.

scholarly journals A mutant tRNA affects delta-mediated transcription in Saccharomyces cerevisiae.

Genetics ◽  
1992 ◽  
Vol 132 (2) ◽  
pp. 361-374
Author(s):  
A M Happel ◽  
F Winston
Keyword(s):  
Genetic Background ◽  
Mutant Gene ◽  
Repeat Sequence ◽  
Gene Products ◽  
Cloning And Sequencing ◽  
Ty Elements ◽  
Extragenic Suppressors ◽  
Insertion Mutations ◽  
Terminal Repeat Sequence ◽  
New Mutations

Abstract Mutations in the SPT3, SPT7, SPT8 and SPT15 genes define one class of trans-acting mutations that are strong suppressors of insertion mutations caused by Ty elements or by the Ty long terminal repeat sequence, delta. These SPT genes are required for normal transcription of Ty elements, and their gene products are believed to be involved in initiation of Ty transcription from delta sequences. We have isolated and analyzed extragenic suppressors of spt3 mutations. These new mutations, named rsp, partially suppress the requirement for SPT3, SPT7, SPT8 and SPT15 functions. In addition, rsp mutations cause changes in transcription of some delta insertions in an SPT+ genetic background. Interactions between mutations in the four identified RSP genes show a number of interesting genetic properties, including the failure of unlinked rsp mutations to complement for recessive phenotypes. Cloning and sequencing of one rsp mutant gene, rsp4-27, showed that it encodes a frameshift suppressor glycine tRNA. Our results indicate that the other three RSP genes also encode frameshift suppressor glycine tRNAs. In addition, other types of frameshift suppressor glycine tRNAs can confer some Rsp- phenotypes.

scholarly journals The MSN1 and NHP6A Genes Suppress SWI6 Defects in Saccharomyces cerevisiae

Genetics ◽  
1999 ◽  
Vol 151 (1) ◽  
pp. 45-55
Author(s):  
Julia Sidorova ◽  
Linda Breeden
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Transcription Factor ◽  
Transcription Factors ◽  
Dna Binding ◽  
Gene Transcription ◽  
Chromatin Structure ◽  
Transcriptional Activator ◽  
Temperature Sensitive ◽  
Gene Products ◽  
Protein Association

Abstract Ankyrin (ANK) repeats were first found in the Swi6 transcription factor of Saccharomyces cerevisiae and since then were identified in many proteins of eukaryotes and prokaryotes. These repeats are thought to serve as protein association domains. In Swi6, ANK repeats affect DNA binding of both the Swi4/Swi6 and Mbp1/Swi6 complexes. We have previously described generation of random mutations within the ANK repeats of Swi6 that render the protein temperature sensitive in its ability to activate HO transcription. Two of these SWI6 mutants were used in a screen for high copy suppressors of this phenotype. We found that MSN1, which encodes a transcriptional activator, and NHP6A, which encodes an HMG-like protein, are able to suppress defective Swi6 function. Both of these gene products are involved in HO transcription, and Nhp6A may also be involved in CLN1 transcription. Moreover, because overexpression of NHP6A can suppress caffeine sensitivity of one of the SWI6 ANK mutants, swi6-405, other SWI6-dependent genes may also be affected by Nhp6A. We hypothesize that Nhp6A and Msn1 modulate Swi6-dependent gene transcription indirectly, through effects on chromatin structure or other transcription factors, because we have not been able to demonstrate that either Msn1 or Nhp6A interact with the Swi4/Swi6 complex.

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