RBMX is a component of the centromere noncoding RNP complex involved in cohesion regulation

Abstract

Satellite I RNA, a noncoding (nc)RNA transcribed from repetitive regions in human centromeres, binds to Aurora kinase B and forms a ncRNP complex required for chromosome segregation. To examine its function in this process, we purified satellite I ncRNP complex from nuclear extracts prepared from asynchronized or mitotic (M) phase-arrested HeLa cells and then carried out LC/MS to identify proteins bound to satellite I RNA. RBMX (RNA-binding motif protein, X-linked), which was isolated from M phase-arrested cells, was selected for further characterization. We found that RBMX associates with satellite I RNA only during M phase. Knockdown of RBMX induced premature separation of sister chromatid cohesion and abnormal nuclear division. Likewise, knockdown of satellite I RNA also caused premature separation of sister chromatids during M phase. The amounts of RBMX and Sororin, a cohesion regulator, were reduced in satellite I RNA-depleted cells. These results suggest that satellite I RNA plays a role in stabilizing RBMX and Sororin in the ncRNP complex to maintain proper sister chromatid cohesion.

DEAH box RNA helicase DHX38 associates with satellite I noncoding RNA involved in chromosome segregation

“…We previously found that Aurora B and RBMX interact with satellite I ncRNA at mitotic phase, indicating that satellite I ncRNA forms an RNP complex with several mitotic regulators to regulate chromosome segregation (Cho et al, ; Ideue et al, ). We used IP experiments to investigate the interaction between DHX38 and satellite I ncRNA.…”

“…We previously reported that human satellite I ncRNA has a role in chromosome segregation (Ideue et al, ). Several protein factors associate with this ncRNA and function as the ncRNP complex (Cho et al, ). We found that DHX38 interacts with human satellite I ncRNA, and depletion of this protein caused defects in chromosome segregation.…”

“…HeLa cells were grown in DMEM supplemented with 10% FBS at 37°C and 5% CO 2 . Synchronization of cells at mitotic phase was carried out by thymidine double block and addition of nocodazole as described (Cho et al, ). We used asynchronized cells as interphase cells in this study, as the majority of asynchronized cells are in the interphase.…”

“…A relationship between Aurora B and centromeric ncRNA has been also reported in other species (Blower, ; Ferri, Bouzinba‐Segard, Velasco, Hube, & Francastel, ; Jambhekar, Emerman, Schweidenback, & Blower, ). Pull‐down experiments identified satellite I ncRNA‐interacting proteins other than Aurora B (Cho, Ideue, Nagayama, Araki, & Tani, ). RBMX, a component of the satellite I ncRNP complex, is involved in sister chromatid cohesion.…”

“…Depletion of RBMX caused chromosome segregation error similar to that of satellite I ncRNA depletion. Depletion of satellite I ncRNA influenced amounts of RBMX protein (Cho et al, ). Therefore, human centromeric ncRNA forms a satellite I RNP complex with mitotic regulators and regulates chromosome segregation by controlling interacting factors.…”