New roles of DNA‐binding and forkhead‐associated domains of Fkh1 and Fkh2 in cellular functions

Abstract

Two yeast forkhead transcription factors Fkh1 and Fkh2 regulate the transcription of CLB2 cluster genes important for mitosis. Both proteins contain a DNA-binding domain (DBD) and a forkhead-associated domain (FHAD), which are essential for ternary complex formation with transcription factor Mcm1, the transcription of CLB2 cluster genes and the physical interaction with Ndd1 and Clb2. Fkh2 also contains an additional C′ domain that contains six consensus Cdk phosphorylation sites, but the function of this domain is dispensable. Here, we found new roles of the DBD, the FHAD, and the C′ domain of Fkh1 and Fkh2 in cellular functions. The Fkh2 DBD determines the genetic interaction with NDD1, while both the FHAD and DBD of Fkh1 or Fkh2 determine cell morphology and stability of their own transcripts. Both HFADs, but not DBDs, also mediate physical interaction between Fkh1 and Fkh2.DBD and HFAD of Fkh1 and DBD, but not HFAD, of Fkh2 are also fundamental for nuclear localization. However, the Fkh2-specific C′ domain has no role in these aspects except in the stability of some fkh mutant transcripts, which is either increased or decreased in the presence of this domain. These findings reveal that Fkh1 and Fkh2 have multiple cellular functions and function mainly via their DBD and FHAD through a domain-controlled feedback regulation mechanism.

Fdo1, Fkh1, Fkh2 and the Swi6-Mbp1 MBF complex regulate Mcd1 levels to impact eco1 rad61 cell growth in Saccharomyces cerevisiae

“…Surprisingly, the deletion of FKH1 failed to revert the temperature sensitivity otherwise exhibited by eco1Δ rad61Δ cells (Figure 6A). The budding yeast genome contains a paralog of Fkh1, termed Fkh2, that exhibits redundant transcriptional roles in cell cycle control (90). Thus, we considered the possibility that Fdo1 impacts cohesin function through Fkh2 instead of Fkh1.…”