Constitutive transcription of yeast ribosomal protein gene TCM1 is promoted by uncommon cis- and trans-acting elements.

In Saccharomyces cerevisiae UV radiation and a variety of chemical DNA-damaging agents induce the transcription of specific genes, including several involved in DNA repair. One of the best characterized of these genes is PHR1, which encodes the apoenzyme for DNA photolyase. Basal-level and damage-induced expression of PHR1 require an upstream activation sequence, UAS PHR1 , which has homology with DRC elements found upstream of at least 19 other DNA repair and DNA metabolism genes in yeast. Here we report the identification of the UME6 gene of S. cerevisiae as a regulator of UAS PHR1 activity. Multiple copies of UME6 stimulate expression from UAS PHR1 and the intact PHR1 gene. Surprisingly, the effect of deletion of UME6 is growth phase dependent. In wild-type cells PHR1 is induced in late exponential phase, concomitant with the initiation of glycogen accumulation that precedes the diauxic shift. Deletion of UME6 abolishes this induction, decreases the steady-state concentration of photolyase molecules and PHR1 mRNA, and increases the UV sensitivity of a rad2 mutant. Despite the fact that UAS PHR1 does not contain the URS1 sequence, which has been previously implicated in UME6-mediated transcriptional regulation, we find that Ume6p binds to UAS PHR1 with an affinity and a specificity similar to those seen for a URS1 site. Similar binding is also seen for DRC elements from RAD2, RAD7, and RAD53, suggesting that UME6 contributes to the regulated expression of a subset of damage-responsive genes in yeast.

Section: Methodsmentioning

confidence: 99%

Role of UME6 in Transcriptional Regulation of a DNA Repair Gene in Saccharomyces cerevisiae

Sweet

Jang

Sancar

1997

“…Surprisingly, ABF1 binding was slightly affected by these mutations, which flank the ABF1 consensus binding site. However, it is not without precedent that mutations or deletions flanking this consensus sequence reduce ABF1 binding (23,36). To test whether the aforementioned mutations affected expression in vivo after growth of the cells on different carbon sources, we compared expression mediated by the wild-type and mutated thiolase promoters with the firefly luciferase cDNA as a reporter.…”

Section: Figmentioning

confidence: 99%

The Upstream Region of theFOX3Gene Encoding Peroxisomal 3-Oxoacyl-Coenzyme A Thiolase inSaccharomyces cerevisiaeContains ABF1- and Replication Protein A-Binding Sites That Participate in Its Regulation by Glucose Repression

Einerhand

Kos

Smart

et al. 1995

Expression of the FOX3 gene, which encodes yeast peroxisomal 3-oxoacyl-coenzyme A thiolase, can be induced by oleate and repressed by glucose. Previously, we have shown that induction was mediated by an oleate response element. Just upstream of this element a negatively acting control region that mediated glucose repression was found. In order to study this negative control region, we carried out DNA-binding assays and analyzed phenotypes of mutations in this region and in the trans-acting factor CAR80, which is identical to UME6. DNA-binding assays showed that two multifunctional yeast proteins, ABF1 and RP-A, interacted with the negative control element independently of the transcriptional activity of the FOX3 gene. ABF1 and RP-A, the latter being identical to BUF, were able to bind to DNA independently of one another but also simultaneously. The phenotypes of mutations in either DNA-binding sites of ABF1, RP-A, or both, which affected the DNA binding of these factors in vitro, indicated that these sites and the proteins that interact with them participate in glucose repression. The involvement of the RP-A site in glucose repression was further supported by our observation that the CAR80 gene product, which is required for repression mediated by the RP-A site, was essential for maintenance of glucose repression. In addition to the RP-A site in the FOX3 promoter, similar sequences were observed in other genes involved in peroxisomal function. RP-A proved to bind to all of these sequences, albeit with various affinities. From these results it is concluded that the ABF1 and RP-A sites are being required in concert to mediate glucose repression of the FOX3 gene. In addition, coordinated regulation of expression of genes involved in peroxisomal function in response to glucose is mediated by proteins associated with the RP-A site, probably RP-A and CAR80.

“…Deletions downstream of the T-rich elements have little effect on the rate of transcription but can affect the initiation site (47). For a small minority of RP genes, including RPL3, RPL4A, RPL4B, and RPS28A, a single Abf1p site replaces the two Rap1p sites (8,13). Nevertheless, such genes appear to be regulated coordinately with the others.…”

mentioning

confidence: 99%

Transcriptional Elements Involved in the Repression of Ribosomal Protein Synthesis

Nierras

Warner

1999

103

The ribosomal proteins (RPs) of Saccharomyces cerevisiae are encoded by 137 genes that are among the most transcriptionally active in the genome. These genes are coordinately regulated: a shift up in temperature leads to a rapid, but temporary, decline in RP mRNA levels. A defect in any part of the secretory pathway leads to greatly reduced ribosome synthesis, including the rapid loss of RP mRNA. Here we demonstrate that the loss of RP mRNA is due to the rapid transcriptional silencing of the RP genes, coupled to the naturally short lifetime of their transcripts. The data suggest further that a global inhibition of polymerase II transcription leads to overestimates of the stability of individual mRNAs. The transcription of most RP genes is activated by two Rap1p binding sites, 250 to 400 bp upstream from the initiation of transcription. Rap1p is both an activator and a silencer of transcription. The swapping of promoters between RPL30 and ACT1 or GAL1 demonstrated that the Rap1p binding sites of RPL30 are sufficient to silence the transcription of ACT1 in response to a defect in the secretory pathway. Sir3p and Sir4p, implicated in the Rap1p-mediated repression of silent mating type genes and of telomere-proximal genes, do not influence such silencing of RP genes. Sir2p, implicated in the silencing both of the silent mating type genes and of genes within the ribosomal DNA locus, does not influence the repression of either RP or rRNA genes. Surprisingly, the 180-bp sequence of RPL30 that lies between the Rap1p sites and the transcription initiation site is also sufficient to silence the Gal4p-driven transcription in response to a defect in the secretory pathway, by a mechanism that requires the silencing region of Rap1p. We conclude that for Rap1p to activate the transcription of an RP gene it must bind to upstream sequences; yet for Rap1p to repress the transcription of an RP gene it need not bind to the gene directly. Thus, the cell has evolved a two-pronged approach to effect the rapid extinction of RP synthesis in response to the stress imposed by a heat shock or by a failure of the secretory pathway. Calculations based on recent transcriptome data and on the half-life of the RP mRNAs suggest that in a rapidly growing cell the transcription of RP mRNAs accounts for nearly 50% of the total transcriptional events initiated by RNA polymerase II. Thus, the sudden silencing of the RP genes must have a dramatic effect on the overall transcriptional economy of the cell.The Saccharomyces cerevisiae cell invests enormous resources in the synthesis of ribosomes. In a rapidly growing cell, the 100 or more rRNA genes are responsible for at least 60% of total transcription (59). The 137 ribosomal protein (RP) genes are among the most active in the genome (57). As a result, the cell has evolved mechanisms that tightly control the synthesis of the components of the ribosome. The 78 RPs are synthesized in nearly equimolar amounts that are matched to the synthesis of rRNA. Furthermore, the synthesis of these components is coo...