Fig. 6. Effect of EGF on ubiquitination of Cx43. IAR20 cells were treated with 100 ng ml^–1 EGF for different lengths of time or preincubated with 50 µM PD98059 for 15 minutes before addition of 100 ng ml^–1 EGF. Cell lysates were subjected to immunoprecipitation with anti-Cx43 antibodies or preimmune serum (PI) as control. Equal amounts of total cell protein were subjected to SDS-PAGE and western blotting using affinity-purified anti-ubiquitin antibodies (top) or anti-Cx43 antibodies (bottom).