FIG. 2.

Deletion and mutational analysis of region C shows that an SCB is necessary for complete RE activity. (A) Sequence comparison of region C among the Saccharomyces sensu stricto species. The MATα2-Mcm1 operator is shown. Sequences enclosed by the box correspond to the SCB necessary for RE activity (reverse complement of the consensus). Only perfectly conserved residues between the five species are indicated in the consensus sequence. (B) (Top) HML usage in strains bearing different mutations in region C. Some of these mutations have been introduced in the 270-bp synthetic RE which lacks region E (lower lane). Others were introduced in the 753-bp minimal RE (upper lane). (Middle) Sequence of region C. The Matα2-Mcm1 operator is underlined, and the SCB is shown in the box. (Bottom) HML usage in strains bearing the 753-bp minimal RE with several deletions of region C sequences.