Spo76p is a conserved chromosome morphogenesis protein that links the mitotic and meiotic programs

Spo76p is conserved and related to the fungal proteins Pds5p and BIMD and t he human AS3 prostate proliferative shutoff-associated protein. Spo76p loca lizes to mitotic and meiotic chromosomes, except at metaphase(s) and anapha se(s). During meiotic prophase, Spo76p assembles into strong lines in corre lation with axial element formation. As inferred from spo76-1 mutant phenot ypes, Spo76p is required for sister chromatid cohesiveness, chromosome axis morphogenesis, and chromatin condensation during critical transitions at m itotic prometaphase and meiotic midprophase. Spo76p is also required for me iotic interhomolog recombination, likely at postinitiation stage(s). We pro pose that a disruptive force coordinately promotes chromosomal axial compac tion and destabilization of sister connections and that Spo76p restrains an d channels the effects of this force into appropriate morphogenetic mitotic and meiotic outcomes.