Fig. 1.

Proteasome inhibition, after fertilization, causes accumulation of ubiquitinated proteins. (A) Schematic diagram of experiments using fertilized oocytes at 1 hpi. (B) Total protein extracts from untreated metaphase II oocytes (MII), untreated 1-cell embryos (1C), untreated 2-cell embryos (2C), MG132-treated (+) MII, and MG132-treated 1C embryos were immunoblotted with anti-Ub antibody. Actin was used as a loading control. Molecular masses (kDa) are shown on the right. (C) Effect of transient MG132 treatment (after fertilization) on the proteasome chymotrypsin-like activity in embryos. Proteasome chymotrypsin-like activity in crude lysate from 100 fresh untreated 1C, 2C, and MG132-treated 1C, were measured using Suc-LLVY-AMC as a substrate. This experiment was performed in triplicate. Statistically significant differences between untreated and MG132-treated embryos are shown (* P < 0.05). Bars represent the standard error of the mean. Untreated (white bars), Treated with MG132 (black bars).