Heat stress-induced Cup9-dependent transcriptional regulation of SIR2.
The epigenetic writer Sir2 maintains the heterochromatin state of chromosome in three chromosomal regions, namely, the silent mating type loci, telomeres, and the ribosomal DNA (rDNA). In this study, we demonstrated the mechanism by which Sir2 is regulated under heat stress. Our study reveals that a transient heat shock causes a drastic reduction in the SIR2 transcript which results in sustained failure to initiate silencing for as long as 90 generations. Hsp82 overexpression, which is the usual outcome of heat shock treatment, leads to a similar downregulation of SIR2 transcription. Using a series of genetic experiments, we have established that heat shock or Hsp82 overexpression causes upregulation of CUP9 that, in turn, represses SIR2 transcription by binding to its upstream activator sequence. We have mapped the cis regulatory element of SIR2. Our study shows that the deletion of cup9 causes reversal of the Hsp82 overexpression phenotype and upregulation of SIR2 expression in heat-induced Hsp82-overexpressing cells. On the other hand, we found that Cup9 overexpression represses SIR2 transcription and leads to a failure in the establishment of heterochromatin. The results of our study highlight the mechanism by which environmental factors amend the epigenetic configuration of chromatin.
Department of Biotechnology and Bioinformatics, School of Life Sciences, University of Hyderabad, Hyderabad, India.
Shyamasree
S
Laskar
Centre for Bioinformatics, University of Kerala, Thiruvanthapuram, India.
Sheeba
S
K
Department of Biochemistry, School of Life Sciences, University of Hyderabad, Hyderabad, India.
Mrinal K
MK
Bhattacharyya
Centre for Bioinformatics, University of Kerala, Thiruvanthapuram, India.
Achuthsankar S
AS
Nair
Centre for Bioinformatics, University of Kerala, Thiruvanthapuram, India.
Pawan
P
Dhar
Department of Biotechnology and Bioinformatics, School of Life Sciences, University of Hyderabad, Hyderabad, India sbtsl@uohyd.ernet.in.
Sunanda
S
Bhattacharyya
D000818:Animals; D015966:Gene Expression Regulation, Fungal / Q000502:physiology*; D018869:Heat-Shock Response; D006570:Heterochromatin / Q000378:metabolism; D018398:Homeodomain Proteins / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae / Q000378:metabolism*; D056565:Sirtuin 2 / Q000378:metabolism*; D016615:Telomere / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology
C090457:CUP9 protein, S cerevisiae; D006570:Heterochromatin; D018398:Homeodomain Proteins; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D014157:Transcription Factors; C087778:SIR2 protein, S cerevisiae; D056565:Sirtuin 2