Loss of function of senataxin (SETX), a bona-fide
RNA/
DNA helicase, is associated with neuronal degeneration leading to
Ataxia and Ocular
Apraxia (AOA) in human patients. SETX is proposed to promote transcription termination, DNA replication, DNA repair, and to unwind deleterious
RNA:
DNA hybrids in the genome. In all the above-mentioned mechanisms, SETX unwinds transcription complex-associated nascent
RNA which is then degraded by the
RNA exosome complex. Here we have used B cells isolated from a SETX mutant mouse model and compared
genomic instability and
immunoglobulin heavy chain locus (IgH) class switch recombination (CSR) to evaluate aberrant and programmed genomic rearrangements, respectively. Similar to
RNA exosome mutant primary B cells, SETX mutant primary B cells display
genomic instability but a modest decrease in efficiency of CSR. Furthermore, knockdown of Setx mRNAs from CH12-F3 B-cell lines leads to a defect in
IgA CSR and accumulation of aberrant patterns of mutations in IgH switch sequences. Given that SETX mutant mice do not recapitulate the AOA neurodegenerative phenotype, it is possible that some aspects of SETX biology are rescued by redundant helicases in mice. Overall, our study provides new insights into the role of the SETX/
RNA exosome axis in suppressing
genomic instability so that programmed DNA breaks are properly orchestrated.