Determining the role of centromeric long non-coding RNA in chromosome segregation in saccharomyces cerevisiae

Abstract

Centromeric DNA sequences are not conserved among organisms and centromeres are proposed to be regulated epigenetically. Centromeric transcription is one of the epigenetic factors identified in many eukaryotes, and increasing evidences indicate that centromeric transcription and its corresponding non-coding RNA may involve in controlling the activity of centromere, ensuring accurate chromosome segregation. The budding yeast S. cerevisiae centromere is originally thought to be DNA sequence-dependent without any epigenetic control. Nonetheless, a recent study showed that transcriptional activity at budding yeast centromere is important for regulating centromere function. Centromeric transcription is cell cycle-dependent and the timing is not conserved. Our preliminary result shows that budding yeast centromere is transcribed during S phase while human centromere transcribed from late mitosis to early G1 phase. Intriguingly, centromeric transcription timing in different organisms is coincident with the centromeric protein A (CENP-A) loading time in the centromere of the corresponding organisms. We propose that the primitive and conserved function of cenRNAs is to promote CENP-A loading and centromeric transcription may involve in controlling the timing of CENP-A deposition. The cell cycle-specific regulation of centromeric transcription in different eukaryotes is still elusive. In budding yeast, we identified a centromeric transcriptional factor Cbf1 and a histone H2A variant Htz1 that repress centromeric transcription, indicating that centromeric transcription is regulated in both DNA and nucleosome level. cbf1Δ and htz1Δ increase cenRNA level and CEN plasmid loss rate, which indicates a disruption of centromere activity. As both proteins bind at the centromeric region, we hypothesized that a release of Cbf1 and Htz1 from the centromere during S phase results in centromeric transcription induction. We will further investigate the regulation and the role of centromeric transcription in centromere function. Our study will help to clarify how the distinct regulation of centromeric transcription regulates a conserved epigenetic mechanism across eukaryotic centromeres and demonstrate how epigenetic mechanisms maintain chromosome stability.