α-Satellite RNA maintains centromeric cohesion through R-loops

Tandemly repeated satellite DNAs provide the building blocks for centromeres, but whether and how their transcripts regulate chromosome segregation remain poorly defined. Here, we show that human α-satellite RNAs (α-SatRNAs) are required for maintaining centromeric cohesion during mitosis. α-SatRNAs localize to centromeres and physically associate with α-satellite chromatin to form R-loops both in cis and in trans. Disruption of these R-loops by RNase H1 overexpression causes centromeric cohesion defects, phenocopying α-SatRNA knockdown, which can be rescued by the expression of an α-satellite consensus sequence, supporting a major role for α-SatRNA-formed R-loops in centromeric cohesion. Furthermore, ectopic targeting of the cohesion protector Shugoshin (Sgo)1 to centromeric α-SatDNAs largely rescues centromeric cohesion defects caused by α-SatRNA knockdown or RNase H1 overexpression. Our findings reveal a critical pathway comprising α-SatRNAs, R-loops, and Sgo1 in regulating centromeric cohesion, thus providing an important mechanism to explain how satellite transcripts regulate chromosomal stability.