Ssb1/2-IntS complexes maintain splicing integrity and genomic stability through regulating RNA Polymerase II mediated snRNA levels

ABSTRACT: Ssb1(NABP2/OBFC2A) and Ssb2 (NABP1/OBFC2B) are two closely related proteins that show functional redundancies supported by their existence in two separate subcomplexes with identical proteins. Ssb1 knockout causes perinatal lethality in mice, Ssb2 knockout does not associate with any observable phenotypes, however, double knockout of both Ssb1/2 causes embryonically lethality. Notably, conditional loss of both in adult mice leads to acute lethality due to bone marrow and gut failure. Here, we further demonstrate that the overlapping essential function of both Ssb1/2 is through their prime binding partner IntS3, a member of the multiprotein complex called the Integrator. The Integrator complex interacts with the largest subunit of RNA Polymerase II and is required for processing and termination of small nuclear RNAs (snRNAs). Here, we provide a firsthand evidence that the stability of the Integrator complex is compromised in mouse-embryonic fibroblasts (MEFs) with compound loss of both Ssbs. We further demonstrate that these MEFs show overexpression of unprocessed snRNAs which forces the cells to express alternative spliced variants of genes that are required for transcription and cell cycle regulation. This phenotype closely phenocopies loss of core integrator subunit, IntS11 as well as splicing components B and C. Interestingly, the phenotype gets partially restored by overexpression of wildtype Ssb1 but not by the Ssb-mutant defective in binding integrator subunit, IntS3, demonstrating the essential roles of Ssb1/2 in the maintenance of the Integrator complex and thereby, genomic stability.

ORGANISM(S): Mus musculus

PROVIDER: GSE155240 | GEO | 2022/03/11

REPOSITORIES: GEO