Deficiency of Polη in Saccharomyces cerevisiae reveals the impact of transcription on damage-induced cohesion

摘要

The structural maintenance of chromosome (SMC) complex cohesin mediates sister chromatid cohesion established during replication, and damage-induced cohesion formed in response to DSBs post-replication. The translesion synthesis polymerase Polη is required for damage-induced cohesion through a hitherto unknown mechanism. Since Polη is functionally associated with transcription, and transcription triggers de novo cohesion in Schizosaccharomyces pombe , we hypothesized that transcription facilitates damage-induced cohesion in Saccharomyces cerevisiae . Here, we show dysregulated transcriptional profiles in the Polη null mutant ( rad30Δ ), where genes involved in chromatin assembly and positive transcription regulation were downregulated. In addition, chromatin association of RNA polymerase II was reduced at promoters and coding regions in rad30Δ compared to WT cells, while occupancy of the H2A.Z variant (Htz1) at promoters was increased in rad30Δ cells. Perturbing histone exchange at promoters inactivated damage-induced cohesion, similarly to deletion of the RAD30 gene. Conversely, altering regulation of transcription elongation suppressed the deficient damage-induced cohesion in rad30Δ cells. Furthermore, transcription inhibition negatively affected formation of damage-induced cohesion. These results indicate that the transcriptional deregulation of the Polη null mutant is connected with its reduced capacity to establish damage-induced cohesion. This also suggests a linkage between regulation of transcription and formation of damage-induced cohesion after replication. Author summary The cohesin complex dynamically associates with chromosomes and holds sister chromatids together through cohesion established during replication. This ensures faithful chromosome segregation at anaphase. In budding yeast, DNA double strand breaks also trigger sister chromatid cohesion after replication. This so-called damage-induced cohesion is formed both close to the breaks, and genome-wide on undamaged chromosomes. The translesion synthesis polymerase eta (Polη) is specifically required for genome wide damage-induced cohesion. Although Polη is well characterized for its function in bypassing ultraviolet-induced DNA lesions, its mechanistic role in damage-induced cohesion is unclear. Here, we show that transcriptional regulation is perturbed in the persistent absence of Polη. We find that Polη preferably associates with certain types of promoters, although its role in transcription might be indirect. By testing mutants that perturb histone exchange or regulation of transcription, as well as through inhibiting transcription, we show that transcriptional deregulation negatively affects formation of damage-induced cohesion. This supports the connection between transcriptional deregulation and deficient damage-induced cohesion in the Polη null mutant. Importantly, our study provides new insight into formation of damage-induced cohesion after replication, which will be interesting to explore further.