Figure 1.

Plasmid-mediated complementation of crl mutants. Cells were streaked on YPD agar plates and incubated at 37°C and 30°C for 3 d. Plasmids containing the CRL3 (SUG1) or the PRE3 gene complement temperature sensitivity of crl3–2 (left side) and crl21 mutants (right side), respectively. Control strains (bottom) contain the empty plasmid pRS316. After 4 d the strain Y55–1162 (crl3–2 ade1) carrying the CRL3 plasmid (wild type) accumulates significant amounts of a red dye (indicated by the darker color of the colonies, 30°C control plate), which is typically found when starving cells which harbor distinct mutations in the adenine biosynthesis pathway. In contrast, crl3–2 mutant cells generate only tiny amounts of this red product.