Co-immunoprecipitation (co-IP)

Cells were resuspended in RIPA lysis buffer, followed by incubation with anti-MTBP (1:100; SC137201, Santa Cruz Biotechnology, Dallas, TX, USA) or anti-MDM2 (1:100; ab16895) overnight at 4°C. Then, the proteins were incubated with protein-A/G PLUS-Agarose beads (Millipore). The samples were further analyzed by western blot analysis and anti-IgG served as a negative control.