Senataxin Plays an Essential Role with DNA Damage Response Proteins in Meiotic Recombination and Gene Silencing

Abstract

Senataxin, mutated in the human genetic disorder ataxia with oculomotor apraxia type 2 (AOA2), plays an important role in maintaining genome integrity by coordination of transcription, DNA replication, and the DNA damage response. We demonstrate that senataxin is essential for spermatogenesis and that it functions at two stages in meiosis during crossing-over in homologous recombination and in meiotic sex chromosome inactivation (MSCI). Disruption of the Setx gene caused persistence of DNA double-strand breaks, a defect in disassembly of Rad51 filaments, accumulation of DNA:RNA hybrids (R-loops), and ultimately a failure of crossing-over. Senataxin localised to the XY body in a Brca1-dependent manner, and in its absence there was incomplete localisation of DNA damage response proteins to the XY chromosomes and ATR was retained on the axial elements of these chromosomes, failing to diffuse out into chromatin. Furthermore persistence of RNA polymerase II activity, altered ubH2A distribution, and abnormal XY-linked gene expression in Setx−/− revealed an essential role for senataxin in MSCI. These data support key roles for senataxin in coordinating meiotic crossing-over with transcription and in gene silencing to protect the integrity of the genome.

Systematic screening reveals a role for BRCA1 in the response to transcription-associated DNA damage

“…Imputed functions of TONSL and known functions of the TONSL-binding FACT complex and of SETX, TCEANC, and TCEA2-all proteins engaged in transcription and/or RNA processing and all proteins that genetically interact with BRCA1-represent new processes through which BRCA1 participates in the prevention and/or repair of DNA damage. That BRCA1 is engaged in transcriptionassociated damage control is supported as a concept by these results and by BRCA1-and BARD1-linked phenomena observed by others (Scully et al 1997;Manley 1999, 2001;Le Page et al 2000;Kleiman et al 2005;Becherel et al 2013;Yuce and West 2013;Bhatia et al 2014). Moreover, data reported here now strongly suggest that BRCA1 responds to DNA damage at sites of stalled or defective transcription to either aid in transcription restart and/or resolve certain damaged structures at these sites.…”

“…S2M; Mischo et al 2011;Skourti-Stathaki et al 2011). BRCA1 and SETX co-occupy sites on selected meiotic chromosomes (XY body), where the possibility of R-loop involvement for both proteins in this setting exists (Becherel et al 2013). We also detected genetic interactions between BRCA1 and each of two transcription elongation factors: TCEANC ( Fig.…”

A SUMO-dependent interaction between Senataxin and the exosome, disrupted in the neurodegenerative disease AOA2, targets the exosome to sites of transcription-induced DNA damage

“…Likewise, a recent study suggests that SETX also resolves R-loop structures formed at sites of collision between the transcription and replication machineries, in conjunction with DNA repair factors (Yuce and West 2013). Consistent with this, disruption of SETX in mice revealed an accumulation of R loops and double-strand breaks (DSBs) in germ cells (Becherel et al 2013). It is also known that SETX plays a role in the DNA damage response after oxidative stress (Suraweera et al 2007).…”

“…Indeed, evidence that AOA2 cells are defective in DNA repair, specifically of DSBs, has been presented (Suraweera et al 2007). SETX has been implicated in this process by its ability to resolve cotranscriptional R-loop structures, which can result from collision of replication forks and the transcriptional machinery and lead to DNA damage and genomic instability (Gan et al 2011;Becherel et al 2013;Yuce and West 2013). While the neuronal cells affected in AOA2 are primarily post-mitotic, R loops leading to genomic instability can be created by multiple mechanisms (Aguilera and Garcia-Muse 2012), and SETX can function in resolving them.…”

A double-edged sword: R loops as threats to genome integrity and powerful regulators of gene expression

“…The role of senataxin in DNA damage response, particularly during mouse male meiosis (spermatogenesis), has been highlighted by analysis of mouse strains with SETX gene knockouts. This study led to a model in which senataxin is proposed to resolve R loops to ensure genome integrity during meiotic recombination (Becherel et al 2013). THO mutants from C. elegans and S. cerevisiae also show defective meiosis and increased DNA damage (Castellano-Pozo et al 2012), pointing toward an evolutionarily conserved mechanism to maintain genome stability during meiosis by preventing formation of these potentially harmful structures.…”