The DNA binding and oligomerization domain of MCM1 is sufficient for its interaction with other regulatory proteins

The MCM1 gene encodes an essential DNA binding protein that, in cooperation with the transactivators alpha 1 and STE12 and the repressor alpha 2, confers mating specificity to haploid yeast cells. We show that the amino-terminal third of the MCM1 protein is sufficient for the physical interaction with these factors. A strain expressing just 98 amino acids encompassing the oligomerization and DNA binding domains of MCM1 is viable and mating competent. This motif exhibits considerable similarity to a domain of the mammalian transcription factor SRF. A 98 amino acid hybrid gene coding for the MCM1 DNA binding domain and SRF dimerization domain is sufficient for viability but not for the expression of mating type specific genes. In vitro binding studies suggest that a region of approximately 50 amino acids of MCM1 is essential for providing contacts with alpha 1, alpha 2 and STE12.