Figure 4.

The PTS1 in the homeodomain of α2 is required for repression of a-specific genes. (A) (Upper) A schematic diagram illustrating the reporter gene system used in this experiment to quantitate repression. A matΔ strain contains a reporter gene construct integrated into the chromosome. In the reporter, upstream regulatory sequences control the activity of the LacZ gene. Here, these regulatory sequences contain an α2/Mcm1 operator. For repression to occur, α2 must bind its operator with Mcm1. In the absence of repression, the strain expresses high levels of β-galactosidase (vector). (Lower) Data from liquid β-galactosidase assays, effectively quantitating the amount of repression. In these experiments, we have conducted liquid β-galactosidase assays, in triplicate, on three unique transformants. Our data agrees with that previously published in ref. 17. (B) α2 and α2 R173A are expressed at comparable levels within the cells. Western blots of whole-cell extracts from the strains used in the liquid β-galactosidase assays above were probed with anti-α2 antibody. wt, wild type.