Residency of PKA isoforms at the EFG1 locus during hyphal induction. During yeast growth, Efg1  and Tpk2 proteins reside on promoter and ORF, respectively, and EFG1 is transcribed at high levels (top). During initiation of hyphal formation, increased cAMP levels activate Tpk isoforms by removing Bcy1 repression and Tpk2 phosphorylates Efg1 . This is followed by rapid removal of both Efg1  and Tpk2 (indicated by open arrows). Subsequently the Tpk1 isoform enters the EFG1 promoter at one of the previous Efg1 binding sequences and the Set3C histone deacetylase  occupies the ORF. Other proteins including Czf1, Sfl1, Sfl2 and Ndt80 are known to bind the EFG1 promoter [12, 25] and may contribute to Tpk-dependent regulation of EFG1 expression.