Functional genomics identifies a requirement of pre‐mRNA splicing factors for sister chromatid cohesion

Abstract

Sister chromatid cohesion mediated by the cohesin complex is essential for chromosome segregation during cell division. Using functional genomic screening, we identify a set of 26 pre-mRNA splicing factors that are required for sister chromatid cohesion in human cells. Loss of spliceosome subunits increases the dissociation rate of cohesin from chromatin and abrogates cohesion after DNA replication, ultimately causing mitotic catastrophe. Depletion of splicing factors causes defective processing of the pre-mRNA encoding sororin, a factor required for the stable association of cohesin with chromatin, and an associated reduction of sororin protein level. Expression of an intronless version of sororin and depletion of the cohesin release protein WAPL suppress the cohesion defect in cells lacking splicing factors. We propose that spliceosome components contribute to sister chromatid cohesion and mitotic chromosome segregation through splicing of sororin pre-mRNA. Our results highlight the loss of cohesion as an early cellular consequence of compromised splicing. This may have clinical implications because SF3B1, a splicing factor that we identify to be essential for cohesion, is recurrently mutated in chronic lymphocytic leukaemia.

Graded requirement for the spliceosome in cell cycle progression

“…11,12 Two interpretations were suggested, either the specific spliceosome components depleted are preferentially required for splicing of these mitotic pre-mRNAs or the sororin and Apc2 pre-mRNAs are particularly difficult to splice and require high spliceosome levels. Our results show that depletion of the core spliceosome SNRPB reduced the protein levels of sororin (Fig.…”

“…These results are in agreement with and extend previously reported roles for other spliceosome components in mitosis. 11,12,31 Different degrees of SNRPB depletion produce distinct cell cycle phenotypes…”

“…1,5 Several genome-wide small interfering RNA (siRNA) screens designed to identify genes with roles in genome maintenance and cell cycle progression have reported a role for spliceosome components in these processes. [6][7][8][9][10][11][12] Mutations in multiple spliceosome subunits have been found in leukemia, myeloid neoplasms, and some solid tumors, 13,14 suggesting that spliceosome defects might promote tumorigenesis perhaps through its roles in genome maintenance and cell division.…”

“…17,18 A connection between the spliceosome and cell cycle progression has been found in many organisms including budding yeast, [19][20][21][22][23][24] fission yeast, [25][26][27] Drosophila, 9,28 chicken, 29 mouse, 30 and human cells. 6,11,12,29,31,32 In human cells, depletion of different spliceosome components with siRNAs results in multiple cell cycle defects, with most siRNAs analyzed eliciting mitotic defects 6,11,12,31 although accumulation of cells in S phase 32 has also been observed. The mitotic defects observed after spliceosome depletion have been linked to splicing defects affecting the chromosome cohesion protein sororin 11,12 and Apc2, 11 a subunit of the anaphase-promoting complex/cyclosome (APC/C) required for mitotic progression.…”

Human cactin interacts with DHX8 and SRRM2 to assure efficient pre-mRNA splicing and sister chromatid cohesion

“…Cactin promotes splicing of sororin pre-mRNA While searching for mis-spliced transcripts that could account for the cellular defects arising upon cactin depletion, the cohesin accessory factor sororin (CDCA5 in Table S1) caught our attention because erroneous splicing of its pre-mRNA was previously reported to cause premature separation of sister chromatids (Oka et al, 2014;Sundaramoorthy et al, 2014;van der Lelij et al, 2014;Watrin et al, 2014), a major phenotype induced by cactin depletion. In our RNA-seq data, reads corresponding to sororin intron 1 were over-represented in cactin-depleted samples as compared with control samples, as well as with sororin introns 2-5 both in cactindepleted and control samples (Fig.…”