Project description:The assembly of nucleosomes by histone chaperones is an important component of transcriptional regulation. Here we have assessed the global roles of the S. pombe HIRA histone chaperone complex. Microarray analysis indicates that inactivation of the HIRA complex results in increased expression of at least 4% of fission yeast genes. HIRA-regulated genes overlap with those which are normally repressed in vegetatively growing cells, such as targets of the Clr6 histone deacetylase and silenced genes located in subtelomeric regions. HIRA is also required for silencing of all 13 intact copies of the Tf2 long terminal repeat (LTR) retrotransposon. However, the role of HIRA is not restricted to bona fide promoters, because it also suppresses non-coding transcripts from solo LTR elements and spurious antisense transcripts from cryptic promoters associated with transcribed regions. Furthermore, the HIRA complex is essential in the absence of the quality control provided by nuclear exosome-mediated degradation of illegitimate transcripts. This suggests that HIRA restricts genomic accessibility, and, consistent with this, the chromosomes of cells lacking HIRA are more susceptible to genotoxic agents that cause double strand breaks. Thus the HIRA histone chaperone is required to maintain the protective functions of chromatin.
Project description:The cells with the impaired Hsp40/Hsp70 chaperone complex Mas5/Ssa2 exhibit a transriptional response that is simillar to that of cells with the elevated levels of the heat-shock factor 1 (Hsf1) or heat-stressed wild type fission yeast cells
Project description:Cells that have been pre-exposed to mild stress (priming stress) acquire transient resistance to subsequent severe stress even under different combinations of stresses. This phenomenon is called cross-tolerance. Although it has been reported that cross-tolerance occurs in many organisms, the molecular basis is not clear yet. Here, we identified slm9+ as a responsible gene for the cross-tolerance in the fission yeast Schizosaccharomyces pombe. Slm9 is a homolog of mammalian HIRA histone chaperone. HIRA forms a conserved complex and gene disruption of other HIRA complex components, Hip1, Hip3, and Hip4, also yielded a cross-tolerance-defective phenotype, indicating that the fission yeast HIRA is involved in the cross-tolerance as a complex. We also revealed that Slm9 was recruited to the stress-responsive gene loci upon stress treatment in an Atf1-dependent manner. The expression of stress-responsive genes under stress conditions was compromised in HIRA disruptants. Consistent with this, Pol II recruitment and nucleosome eviction at these gene loci were impaired in slm9D cells. Furthermore, we found that the priming stress enhanced the expression of stress-responsive genes in wild-type cells that were exposed to the severe stress. These observations suggest that HIRA functions in stress response through transcriptional regulation. To determine whether fission yeast HIRA specifically regulates stress-responsive genes under stress condition, we performed genome-wide analysis by using Affymetrix GeneChip oligonucleotide microarrays. Fission yeast cells (WT, slm9D, hip1D) were grown in quadruplicate at 32°C to the logarithmic phase and an aliquot was collected as the unstressed control. The other three aliquots were exposed to 40°C for 1 h, 25 mM H2O2 for 1 h, or 40°C for 1 h followed by 25 mM H2O2 for 1 h, respectively. Total RNA was purified and all the 12 RNA samples were analyzed with GeneChip Yeast Genome 2.0 Array (Affymetrix).
Project description:The cells with the impaired Hsp40/Hsp70 chaperone complex Mas5/Ssa2 exhibit a transriptional response that is simillar to that of cells with the elevated levels of the heat-shock factor 1 (Hsf1) or heat-stressed wild type fission yeast cells A total of 6 experimental conditions has been analyzed including control samples, no replicates were made
