FIGURE 1: Working model for Hos2-dependent regulation of mating.

During yeast-like growth and in the absence of cAMP (left), expression of prf1 and its target genes at the a mating-type loci is maintained at a low basal level just to allow cells of opposite mating types to be able to recognize each other. Hos2 binding to the gene bodies of mating genes might help to maintain this basal expression. During mating or after the addition of cAMP (right), the expression of prf1 and a genes increases significantly. Concomitantly, Hos2 binding to the gene bodies of a genes increases too, probably contributing to their transcriptional elongation and thus allowing efficient mating. Though Hos2 binding to the prf1 gene body remains constant, it decreases at the UAS of its promoter. A plausible explanation for these results is the existence of a long non-coding RNA that inhibits prf1 expression during yeast-like growth (grey lines and arrows).