[Show abstract][Hide abstract] ABSTRACT: Activation of the CLB gene cluster through the assembly of Mcm1p-Fkh2p complexes at target promoters is essential for mitotic entry and transition through M phase. We show that the activation of this mitotic transcriptional program is dependent on the recruitment of Ndd1p, a coactivator that performs its essential function by acting through Fkh2p. Although an essential gene, NDD1 is dispensable in cells expressing a truncated form of Fkh2p lacking its C terminus. When phosphorylated on T319, Ndd1p is recruited to CLB cluster promoters by association with the forkhead-associated (FHA) domain of Fkh2p. Substitution of T319 for alanine significantly reduces recruitment of Ndd1p, resulting in loss of normal transcriptional regulation, severe impairment of cell growth, and a budding defect reminiscent of cells with a Cdk-Clb kinase deficiency. Finally, we show that phosphorylation of T319 and recruitment of Ndd1p to CLB2 and SWI5 promoters is dependent on Cdc28-Clb kinase activity. These data provide a model describing the activation of G2/M transcription through the phosphorylation of Ndd1p by Cdc28-Clb kinase activity.
Genes & Development 08/2003; 17(14):1789-802. DOI:10.1101/gad.1074103 · 12.64 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The 'CLB2 cluster' in Saccharomyces cerevisiae consists of approximately 33 genes whose transcription peaks in late G2/early M phase of the cell cycle. Many of these genes are required for execution of the mitotic program and then for cytokinesis. The transcription factor SFF (SWI5 factor) is thought to regulate a program of mitotic transcription in conjunction with the general transcription factor Mcm1p. The identity of SFF has yet to be determined; hence further understanding of the mechanisms that regulate entry to M phase at the transcriptional level requires characterization of SFF at the molecular level.
We have purified the biochemical activity corresponding to SFF and identified it as the forkhead transcription factor Fkh2p. Fkh2p assembles into ternary complexes with Mcm1p on both the SWI5 and CLB2 cell-cycle-regulated upstream activating sequence (UAS) elements in vitro, and in an Mcm1 p-dependent manner in vivo. Another closely related forkhead protein, Fkh1p, is also recruited to the CLB2 promoter in vivo. We show that both FKH1 and FKH2 play essential roles in the activation of the CLB2 cluster genes during G2-M and in establishing their transcriptional periodicity. Hence, Fkh1p and Fkhp2 show the properties expected of SFF, both in vitro and in vivo.
Forkhead transcription factors have redundant roles in the control of CLB2 cluster genes during the G2-M period of the cell cycle, in collaboration with Mcm1p.
Current Biology 08/2000; 10(15):896-906. DOI:10.1016/S0960-9822(00)00618-7 · 9.92 Impact Factor