The fork head transcription factor Hcm1p participates in the regulation of SPC110, which encodes the calmodulin-binding protein in the yeast spindle pole body.

We previously identified HCM1 as a dosage-dependent suppressor of a calmodulin temperature-sensitive mutant (cmd1-1). Calmodulin performs multiple functions in yeast. Here we demonstrate that the effects of HCM1 are specific to the role of calmodulin at the spindle pole body. Overexpression of HCM1 fully suppresses the temperature sensitivity of a calmodulin mutant (cmd1-3) that only has defects in assembly of the spindle pole body but does not suppress the temperature sensitivity of a calmodulin mutant (cmd1-8) that only affects other functions of calmodulin. The DNA binding specificity of Hcm1p was determined by a selection, amplification and binding protocol. The consensus sequence for an Hcmlp binding site is WAAYAAACAAW. Mutations in the DNA binding domain of Hcm1p abolish the ability of Hcmlp to specifically recognize this binding site and abolish the ability of Hcm1p to act as a suppressor of calmodulin mutants. The promoter of SPC110 contains a match to the consensus binding site. Deletion of HCM1 does not affect the basal level of SPC110 transcription, but reduces the induction that occurs late in G1 of the cell cycle.