Mahanine degrades DNMTs via the ubiquitin-proteasomal pathway. A. PC3 cells were treated with 10 μM mahanine and 20 μM Z-VAD-FMK for 24 hours after which cellular protein lysates were subjected to Western blot analysis to detect DNMT1 and DNMT3B protein levels, β-actin was used as a loading control. B. Chymotrypsin-like proteasomal activity was measured in PC3 cells treated as indicated with mahanine and MG132 for 24 hours. Columns, mean; bars, SEM. *p < 0.05, significantly different from DMSO control. C. LNCaP and PC3 cells were treated with the indicated doses of mahanine for 24 hours with or without MG132 (5 μM). Cell lysates were analyzed for DNMT1 and DNMT3B expression by Western blot. β-actin was used as a loading control. D. PC3 cells were treated with MG132 (5 μM) in the absence and presence of mahanine (10 μM) for 24 hours. Cell lysates were subjected to immunoprecipitation (IP) of DNMT1 or DNMT3B and immunoblotted (IB) for poly-ubiquitin, DNMT1 and DNMT3B.