Project description:Genome wide map of heterochromatin state in fission yeast Schizosaccharomyces pombe via 4 different strains Examination of a single histone modification in 4 different fission yeast strains
Project description:The dynamic nature of genome organization impacts critical nuclear functions including the regulation of gene expression, replication and DNA damage repair. Despite significant progress, the mechanisms responsible for reorganization of the genome in response to cellular stress, such as aberrant DNA replication, are poorly understood. Here we show that fission yeast cells carrying a mutation in the DNA binding protein Sap1 show defects in DNA replication progression and genome stability, and display extensive changes in genome organization.
Project description:R-loops both threaten genome integrity and act as physiological regulators of gene expression and chromatin patterning. To characterize R-loop forming loci in the fission yeast, we used the S9.6-based DRIPc-seq approach to obtain improved strand-specific maps of R-loop forming loci at near nucleotide resolution. We show that the weak affinity of the S9.6 antibody for double-stranded RNA (dsRNA) is sufficient to confound the mapping of genuine R-loops by this approach. dsRNA elimination allowed the identification of two distinct classes of R-loops that differ by their sensitivity to endogenous RNase H activity. Both classes associate with common chromatin features, which are similar to those associated with R-loop formation in human. We used RNA-seq to identify transcripts whose steady-state levels were affected by genome-wide manipulation of R-loop levels. gdh2 is such a transcript and we show that extra RNase H1 stimulates the cis-acting transcription interference between an upstream non-coding RNA and gdh2. Surprisingly, we found that most transcripts whose levels were altered by in vivo manipulation of R-loop levels did not form R-loops. Conversely, the abundance of only few R-loop forming transcripts was impacted by genome-wide variation of R-loop levels. We conclude that prolonged manipulation of R-loop levels imparts indirect effects on the transcriptome that could complicate the use of this strategy to understand R-loop functions.
