FIG. 5.

Yng2p is required for p53 transactivation function in S. cerevisiae but has no effect on Gal1 induction. (A) The strains QY204 (WT) and QY203 (Δyng2), each containing a reporter plasmid encoding His3p under the control of p21 promoter, were transformed with empty vector (−) or a plasmid constitutively expressing p53. Cultures of these strains were grown in minimal medium supplemented with the corresponding auxotrophy to an OD of 1 and then shifted to YPD (OD = 0.1) and grown to a final OD of 1. Total RNA was extracted and Northern blotting was performed using HIS3 and ACT1 probes. The p53-dependent p21-HIS3 activation is lost in the absence of Yng2p (compare lanes 2 and 4). Expression of p53 was monitored by Western blot on whole-cell extracts from each strain. (B) Transcriptional activation of the GAL1 gene does not require Yng2p. Cultures of strains QY204 (WT) and QY203 (Δyng2) were grown in YPD medium to an OD of 1 (lane 1 and 3) and then shifted to YP-galactose medium (lane 2 and 4) for 10 h. Aliquots were taken before and after galactose induction, and total RNA was extracted and analyzed by Northern blots by using a GAL1 probe. The membrane was stained with methylene blue, and 25S rRNA is shown to demonstrate equal loading between lanes. Induction of GAL1 was not affected by deletion of YNG2 (compare lanes 2 and 4).