Figure 3.

Hmg2p ubiquitination was regulated by the mevalonate pathway. (A) Cultures of RHY416 coexpressing Hmg2p and myc-Ub were preincubated with or without lovastatin (25 μg/ml) for 30 min, followed by the IP/IB assay for coprecipitated myc-Ub. An isogenic strain expressing only myc-Hmg2p was run in parallel (myc-Hmg2p) as an assay control and a size standard. (B) The procedure was used to compare several drugs that affect Hmg2p degradation. Both L-659,699 and lovastatin (LOV) stabilize Hmg2p (2), whereas ZA hastens degradation (ref. 2 and see below). The actions of each agent are depicted in mevalonate pathway diagram at bottom: L-659,699 blocks HMG-CoA synthase, LOV blocks HMG-CoA reductase, and ZA blocks squalene synthase.