Figure 6.

A model of DNA damage checkpoint that involves both BRCA1 and ERK1/2. The current understanding of protein signaling pathways involved in DNA damage induced G₂-M checkpoint control are indicated by solid lines. Dashed lines indicate a feedback regulatory loop between ERK1/2 and BRCA1 in the cellular response to IR exposure, as identified by the studies presented in this report. Results in this report also suggest that both BRCA1 and ERK1/2 play important roles in the activation of ATR after IR exposure. In addition, studies in this report indicate an essential role for BRCA1 in IR-induced Chk2 activation.