Genome-wide Analysis of the Functions of a Conserved Surface on the Corepressor Tup1

Abstract

The general transcriptional repressor Tup1 is responsible for the regulation of a large, diverse set of genes in Saccharomyces cerevisiae, and functional homologues of Tup1 have been identified in many metazoans. The crystal structure for the C-terminal portion of Tup1 has been solved and, when sequences of Tup1 homologues from fungi and metazoans were compared, a highly conserved surface was revealed. In this article, we analyze five point mutations that lie on this conserved surface. A statistical analysis of expression microarrays demonstrates that the mutant alleles are deficient in the repression of different subsets of Tup1-regulated genes. We were able to rank the mutant alleles of TUP1 based on the severity of their repression defects measured both by the number of genes derepressed and by the magnitude of that derepression. For one particular class of genes, the mutations on the conserved surface disrupted recruitment of Tup1 to the repressed promoters. However, for the majority of the genes derepressed by the Tup1 point mutants, recruitment of Tup1 to the regulated promoters is largely unaffected. These mutations affect the mechanism of repression subsequent to recruitment of the complex and likely represent a disruption of a mechanism that is conserved in fungi and metazoans. This work demonstrates that the evolutionarily conserved surface of Tup1 interacts with two separate types of proteinssequence-specific DNA-binding proteins responsible for recruiting Tup1 to promoters as well as components that are likely to function in a conserved repression mechanism.

Spreading of a Corepressor Linked to Action of Long-Range Repressor Hairy

“…Thus, it is possible that Hairy-mediated repression does interfere with the binding of some activators on endogenous loci. However, repression can be quite effective even in the absence of activator displacement, perhaps by targeting the basal machinery, similarly to Tup1-mediator interactions seen in yeast (30,17,19). The promoter-proximal location of the repressor in our system might bias the system to such interactions, but this arrangement is physiologically relevant, as Hairy is found in such proximal locations on endogenous genes.…”

A role in the regulation of transcription by light for RCO-1 and RCM-1, the Neurospora homologs of the yeast Tup1–Ssn6 repressor

“…This is a key residue for Tup1 activity since a Ser647Pro mutation in TUP1 resulted in derepression of the heme-repressed ANB1 gene (Carrico and Zitomer, 1998). The WD repeats in Tup1 form a seven-bladed beta propeller structure (Sprague et al, 2000) that mediates the interaction between Tup1-Ssn6 and other regulatory proteins (Green and Johnson, 2005;Komachi et al, 1994). Our results suggest that this protein-interaction motif is relevant for RCO-1 activity in the regulation by light of transcription.…”

Roles of Candida albicans Sfl1 in Hyphal Development

“…(10). Sfl1 inhibits transcription by recruiting Ssn6-Tup1, which is responsible for the repression of over 180 genes in S. cerevisiae (20). The Ssn6-Tup1 complex represses multiple subsets of genes when recruited to promoters by sequence-specific DNA binding repressors (30).…”