Figure 1.

Interaction of Ape and Polβ in the yeast two-hybrid system. (Left) Schematic of plasmids present in indicator strain Y190 (20). Plasmid pAS1–Ape encodes the Gal4_DB–Ape fusion; pACT–Polβ encodes the Gal4_AD–Polβ fusion; pSE1111 encodes a Gal4_AD-Snf4 fusion; pSE1112 encodes a Gal4_DB-Snf1 fusion (19). (Center) Indicator plate for β-galactosidase expression from a GAL promoter-lacZ fusion and His⁺ selection from a GAL promoter-HIS3 fusion. (Right) Quantitation of β-galactosidase expression by a fluorescent assay. Ape-DBD is the Gal4_DB–Ape fusion, Polβ-AD the Gal4_AD–Polβ fusion. Six independent cotransformants of pAS1-Ape and pACT-Polβ were assayed for β-galactosidase activity; single isolates of the other transformants were assayed. An S. cerevisiae lacZ⁺ strain (obtained from R. Brennan and R. H. Schiestl, Harvard School of Public Health, Boston) was assayed as a positive control.