Highlights d Wild-type spatial positioning and timely initiation of recombination require ANKRD31 d Selective use of PRDM9 binding sites as DSB sites requires ANKRD31 d Enrichment of pro-DSB factors in the PAR requires ANKRD31 but not IHO1 d Recombination in the PAR depends on ANKRD31

Orderly segregation of chromosomes during meiosis requires that crossovers form between homologous chromosomes by recombination. Programmed DNA double-strand breaks (DSBs) initiate meiotic recombination. We identify ANKRD31 as a critical component of complexes of DSB-promoting proteins which assemble on meiotic chromosome axes. Genome-wide, ANKRD31 deficiency causes delayed recombination initiation. In addition, loss of ANKRD31 alters DSB distribution owing to reduced selectivity for sites that normally attract DSBs.Strikingly, ANKRD31 deficiency also abolishes uniquely high rates of recombination that normally characterize pseudoautosomal regions (PARs) of X and Y chromosomes.Consequently, sex chromosomes do not form crossovers leading to chromosome segregation failure in ANKRD31-deficient spermatocytes. These defects are accompanied by a genome-wide delay in assembling DSB-promoting proteins on axes and a loss of a specialized PAR-axis domain that is highly enriched for DSB-promoting proteins. Thus, we propose a model for spatiotemporal patterning of recombination by ANKRD31-dependent control of axis-associated complexes of DSB-promoting proteins. Highlights (85 characters max)Temporal and spatial patterning of recombination are regulated by ANKRD31 Selective use of PRDM9 binding sites as DSB hotspots requires ANKRD31 Enrichment of pro-DSB factors in the PAR requires ANKRD31 but not IHO1 Recombination in the PAR critically depends on ANKRD31 are consistent with unpublished data of Acquaviva, Jasin & Keeney (personal communication).Acquaviva et al. observed ANKRD31 aggregates on PARs, and identified chromosome 4, 9 and 13 as autosomes whose non-centromeric ends carry arrays of PAR-like sequences that associate with ANKRD31 aggregates. Distinct molecular requirements for ANKRD31 aggregates and ANKRD31 fociGiven their distinct behaviour in synapsed regions, foci and aggregates of ANKRD31/MEI4/REC114 might represent qualitatively different protein complexes with distinct underlying molecular requirements. To test this possibility we compared localization of ANKRD31, REC114 and MEI4 in Mei4 -/-, Rec114 -/and Iho1 -/spermatocytes ( Figure 2J and S3E-I). The numbers of REC114 and MEI4 foci are strongly reduced in Mei4 -/and Rec114 -/mice, respectively (Kumar et al., 2018). In addition, we found that both focus and aggregate formation of ANKRD31, REC114 and MEI4 were each disrupted in Mei4 -/and Rec114 -/spermatocytes ( Figure S3E-G and Table S3). Remarkably, only the formation of ANKRD31 ( Figure 2I), MEI4 and REC114 foci (Stanzione et al., 2016), but not aggregates, were disrupted in Iho1 -/spermatocytes ( Figure 2J). ANKRD31 aggregates formed efficiently in Iho1 -/spermatocytes; median numbers of ANKRD31 aggregates were four in both wild type (n=62) and Iho1 -/-(n=57) spermatocytes in zygotene. These aggregates always colocalized with aggregates of MEI4 (n=100) and REC114 (n=100) in Iho1 -/spermatocytes ( Figure 2J and S3H).ANKRD31 aggregates also colocalized with PAR FISH signals in late zygotene-like Iho1 -/spe...

In , zygotic genome activation occurs in pre-blastoderm embryos during rapid mitotic divisions. How the transcription machinery is coordinated to achieve this goal in a very brief time span is still poorly understood. Transcription factor II H (TFIIH) is fundamental for transcription initiation by RNA polymerase II (RNAPII). Herein, we show the dynamics of TFIIH at the onset of transcription in embryos. TFIIH shows an oscillatory behaviour between the nucleus and cytoplasm. TFIIH foci are observed from interphase to metaphase, and colocalize with those for RNAPII phosphorylated at serine 5 (RNAPIIS5P) at prophase, suggesting that transcription occurs during the first mitotic phases. Furthermore, embryos with defects in subunits of either the CAK or the core subcomplexes of TFIIH show catastrophic mitosis. Although, transcriptome analyses show altered expression of several maternal genes that participate in mitosis, the global level of RNAPIIS5P in TFIIH mutant embryos is similar to that in the wild type, therefore, a direct role for TFIIH in mitosis cannot be ruled out. These results provide important insights regarding the role of a basal transcription machinery component when the zygotic genome is activated.

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