Evidence for preferential multiplication of the internal unit in tandem repeats of the mating factor alpha genes in Saccharomyces yeasts.

We have determined DNA sequences of the mating factor alpha genes of Saccharomyces uvarum and Saccharomyces italicus and compared them to that of the MF alpha 1 gene of S. cerevisiae. The DNA sequences of the mating factor genes in both species were almost completely identical to that of the MF alpha 1 gene of S. cerevisiae except for the number of tandem repeated units; these latter consisted of a spacer peptide and a mature mating factor and there were three units in S. uvarum and five units in S. italicus compared with four units in the MF alpha 1 of S. cerevisiae. From the detailed comparison of DNA sequences of the spacer peptide-mating factor units from these three species, the high sequence homology can be recognized in the internal units of the tandem repeats. This suggests that the internal units might be multiplied preferentially in the tandem repeated units of mating factor genes.