Figure 4.
STUB1 functions as an E3 ligase for cyclin A. MDA-MB 231 cells were transfected with negative control or STUB1 siRNA, and treated with 20 mM metformin for 24 h. STUB1+/+ and STUB1-/- MEFs were gifts from Dr. Patterson. (A) The protein levels of Cyclin A, E, and D1 in cell lysates were detected by western blot. (B) The mRNA level of Cyclin A was examined by qRT-PCR. (C) Endogenous interaction between STUB1 and Cyclin A was detected in MDA-MB 231 cells. (D) Cyclin A protein level was determined in MEFs after MG132 treatment. (E) Cyclin A Ub assay was performed in wild-type and STUB1-/-MEFs. (F) The level of phospho-AMPK T172 was detected by western blot.