Dbp7 interacts with RNA exosome component Dis3 to mediate CENP-A loading to centromeres

Centromeres are crucial for proper chromosome segregation during cell division. Centromeres in most eukaryotes are epigenetically defined by the histone H3 variant, CENP-A. Centromeric regions are typically transcribed into non-coding RNAs that contribute to centromere functions. However, the precise role of centromeric RNAs in CENP-A loading, in particular the formation of R-loops, remains poorly understood and the mechanisms that safeguard centromeres from R-loop-associated defects are still largely unclear.

Using a visual genetic screen in fission yeast, we find that a conserved ATP-dependent RNA helicase Dbp7, an RNA binding protein that plays a role in preventing accumulation of R-loops at centromeres, is a critical regulator of CENP-A loading to centromeres. Deletion of dbp7⁺ results in CENP-A mislocalization, defects in chromosome segregation, and impaired centromere silencing. Domain-deletion analysis demonstrates that both DEAD-box helicase domain and the C-terminal extension motif contribute to its centromere function. We further show that its catalytic activity is crucial for its role at centromeres. Mechanistically, Dbp7 interacts with the key exosome subunit Dis3, which promotes CENP-A centromere loading by interacting with the CENP-A chaperone Sim3.

Together, this study uncovers a previously unrecognized CENP-A loading mechanism, by which Dbp7 and Dis3 act together to bind to centromeric transcripts and in turn mediate recruitment of CENP-A via the CENP-A chaperone Sim3, providing mechanistic insight into R-loop resolution at centromeres.