The conserved histone deacetylase R pd3 and the DNA binding regulator U me6 repress BOI 1 's meiotic transcript isoform during vegetative growth in S accharomyces cerevisiae

Summary BOI 1 and BOI 2 are paralogs important for the actin cytoskeleton and polar growth. BOI 1 encodes a meiotic transcript isoform with an extended 5′‐untranslated region predicted to impair protein translation. It is, however, unknown how the isoform is repressed during mitosis, and if B oi1 is present during sporulation. By interpreting microarray data from MAT a cells, MAT a/α cells, a starving MAT α/α control, and a meiosis‐impaired rrp6 mutant, we classified BOI 1 's extended isoform as early meiosis‐specific. These results were confirmed by RNA ‐ S equencing, and extended by a 5′‐ RACE assay and N orthern blotting, showing that meiotic cells induce the long isoform while the mitotic isoform remains detectable during meiosis. We provide evidence via motif predictions, an in vivo binding assay and genetic experiments that the R pd3/ S in3/ U me6 histone deacetylase complex, which represses meiotic genes during mitosis, also prevents the induction of BOI 1 's 5′‐extended isoform in mitosis by direct binding of U me6 to its URS 1 target. Finally, we find that Boi1 protein levels decline when cells switch from fermentation to respiration and sporulation. The histone deacetylase R pd3 is conserved, and eukaryotic genes frequently encode transcripts with variable 5′‐ UTRs . Our findings are therefore relevant for regulatory mechanisms involved in the control of transcript isoforms in multi‐cellular organisms.