The RNA-binding protein FUS/TLS interacts with SPO11 and PRDM9 and localize at meiotic recombination hotspots

Abstract

In mammals, meiotic recombination is initiated by the introduction of DNA double strand breaks (DSBs) into narrow segments of the genome, defined as hotspots, which is carried out by the SPO11/TOPOVIBL complex. A major player in the specification of hotspots is PRDM9, a histone methyltransferase that, following sequence-specific DNA binding, generates trimethylation on lysine 4 (H3K4me3) and lysine 36 (H3K36me3) of histone H3, thus defining the hotspots. PRDM9 activity is key to successful meiosis, since in its absence DSBs are redirected to functional sites and synapsis between homologous chromosomes fails. One protein factor recently implicated in guiding PRDM9 activity at hotspots is EWS, a member of the FET family of proteins that also includes TAF15 and FUS/TLS. Here, we demonstrate that FUS/TLS partially colocalizes with PRDM9 on the meiotic chromosome axes, marked by the synaptonemal complex component SYCP3, and physically interacts with PRDM9. Furthermore, we show that FUS/TLS also interacts with REC114, one of the axis-bound SPO11-auxiliary factors essential for DSB formation. This finding suggests that FUS/TLS is a component of the protein complex that promotes the initiation of meiotic recombination. Accordingly, we document that FUS/TLS coimmunoprecipitates with SPO11 in vitro and in vivo. The interaction occurs with both SPO11β and SPO11α splice isoforms, which are believed to play distinct functions in the formation of DSBs in autosomes and male sex chromosomes, respectively. Finally, using chromatin immunoprecipitation experiments, we show that FUS/TLS is localized at H3K4me3-marked hotspots in autosomes and in the pseudo-autosomal region, the site of genetic exchange between the XY chromosomes.

The proper interplay between the expression of Spo11 splice isoforms and the structure of the pseudoautosomal region promotes XY chromosomes recombination

“…Alternatively, SPO11α interacting with both ANKRD31 and REC114 could serve as an intermediary in the interaction of the SPO11β/TOPOVIBL heterotetramer with the PAR. In this regard, we recently demonstrated that SPO11α co-immunoprecipitates with REC114 in vivo [ 48 ], indicating that when this short form of SPO11 is expressed, it interacts with pre-DSB promoting factors, likely promoting DSB activity at the PAR. More studies will be needed to clarify how SPO11 splice isoforms interact dynamically with TOPOVIBL and/or additional type B-like proteins, as well as with RMMAI proteins while cells progress through prophase I.…”

Recent advances in mechanisms ensuring the pairing, synapsis and segregation of XY chromosomes in mice and humans

“…TOPOVIBL interacts directly with REC114 [ 66 ], possibly targeting the function of SPO11/TOPOVIBL onto axis. EWS1 may reinforce the role of FUS and TOPOVIBL via its interaction with PRDM9 and/or SPO11 (adapted from [ 103 ]) …”

“…Previous studies have demonstrated that Ewsr1 −/− spermatocytes are deficient in synapsis of the autosomes and XY chromosomes, indicating their essential function during meiosis [ 101 , 102 ]. By using the Spo11βki -only and Spo11αki -only models [ 30 ], we demonstrated that EWSR1 co-immunoprecipitates with SPO11β, SPO11α and REC114 [ 103 ]. Given the significance of SPO11α in DSB formation at the PAR [ 30 ], this observation supports a role for EWS1 in XY recombination.…”

“…Intriguingly, homolog synapsis is also defective in spermatocytes lacking FUS/TLS expression [ 104 ]. FUS also co-immunoprecipitates with SPO11 splice isoforms and with REC114, and it localizes at the PAR hotspot [ 103 ]. Therefore, FUS/TLS is also a likely player in XY recombination.…”

“…Based on the yeast model, which predicts that the DSB machinery assembled on the axis captures and breaks DNA loops, it has been proposed that in mammals, DSB occurs in PRDM9-marked regions on DNA loops, which are next attached to the axis, where DSBs are made and repaired by assembly of DNA repair factors [ 105 , 106 ]. Both EWSR1 and FUS/TLS co-immunoprecipitates with PRDM9 in spermatocytes [ 103 , 107 ] Therefore, it is speculated that these protein factors binding PRDM9 on chromatin loops are tethered to the axis (bound REC114) and with SPO11, promoting DSB formation [ 103 ]. In mice DSBs form in the PAR independently from PRDM9 [ 75 ].…”