The Enigmatic Conservation of a Rap1 Binding Site in the Saccharomyces cerevisiae HMR-E Silencer

G3: Genes, Genomes, Genetics

Leonid Teytelman¹  Jasper Rine¹  Bilge Özaydin¹  Erin A. Osborne Nishimura¹  Michael B. Eisen² 

[1] Department of Molecular and Cell Biology and California Institute for Quantitative BiosciencesDepartment of Molecular and Cell Biology and California Institute for Quantitative BiosciencesDepartment of Molecular and Cell Biology and California Institute for Quantitative Biosciences;Department of Molecular and Cell Biology and California Institute for Quantitative BiosciencesHoward Hughes Medical Institute, University of California, Berkeley, California 94720Department of Molecular and Cell Biology and California Institute for Quantitative BiosciencesDepartment of Molecular and Cell Biology and California Institute for Quantitative BiosciencesHoward Hughes Medical Institute, University of California, Berkeley, California 94720Howard Hughes Medical Institute, University of California, Berkeley, California 94720Department of Molecular and Cell Biology and California Institute for Quantitative BiosciencesHoward Hughes Medical Institute, University of California, Berkeley, California 94720

关键词: silencing;    sensu stricto;    Rap1;    genomics;    transcription factors;   

DOI  :  10.1534/g3.112.004077

学科分类：生物科学（综合）

来源: Genetics Society of America

【 摘 要 】

Silencing at the HMR and HML loci in Saccharomyces cerevisiae requires recruitment of Sir proteins to the HML and HMR silencers. The silencers are regulatory sites flanking both loci and consisting of binding sites for the Rap1, Abf1, and ORC proteins, each of which also functions at hundreds of sites throughout the genome in processes unrelated to silencing. Interestingly, the sequence of the binding site for Rap1 at the silencers is distinct from the genome-wide binding profile of Rap1, being a weaker match to the consensus, and indeed is bound with low affinity relative to the consensus sequence. Remarkably, this low-affinity Rap1 binding site variant was conserved among silencers of the sensu stricto Saccharomyces species, maintained as a poor match to the Rap1 genome-wide consensus sequence in all of them. We tested multiple predictions about the possible role of this binding-site variant in silencing by substituting the native Rap1 binding site at the HMR-E silencer with the genome-wide consensus sequence for Rap1. Contrary to the predictions from the current models of Rap1, we found no influence of the Rap1 binding site version on the kinetics of establishing silencing, nor on the maintenance of silencing, nor the extent of silencing. We further explored implications of these findings with regard to prevention of ectopic silencing, and deduced that the selective pressure for the unprecedented conservation of this binding site variant may not be related to silencing.

【 授权许可】

Unknown