Figure 2. pUL21a reduces cyclin A protein levels.

(A) MRC-5 cells were mock infected or infected with indicated recombinant HCMV. Cell lysates were collected at 24, 48, or 72 hpi, and analyzed by immunoblotting. IE1 and actin were used as infection and loading controls, respectively. (B) MRC-5 cells were infected as in A with indicated recombinant HCMV. Cell lysates were collected at 48 hpi and analyzed by immunoblotting. (C) MRC-5 cells were infected as in A with indicated HCMV. Cell lysates were collected at indicated times and analyzed by immunoblotting. * indicates nonspecific cross-reacting bands. (D) MRC-5 cells expressing wildtype pUL21a (UL21a) or RxL mutant (UL21a_RxL-AxA) under a tetracycline-inducible promoter were created by lentiviral transduction. Transduced cells were serum-starved for 24 hours, then treated with or without tetracycline (1 µg/ml) for 24 hours and re-stimulated with serum to induce cyclin A expression. Cell lysates were collected at 0 or 24 hours post serum stimulation and analyzed by immunoblotting.