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 HCMI 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 HCMI are specific to the role of calmodulin at the spindle pole body. Overexpression of HCMI 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 Hcm1p binding site is WAAYAAACAAW. Mutations in the DNA binding domain of Hcm1p abolish the ability of Hcm1p 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 HCMI does not affect the basal level of SPC110 transcription, but reduces the induction that occurs late in G(1) of the cell cycle. (C) 1998 Elsevier Science B.V. All rights reserved.