Interaction of rat Cdc37-related protein with retinoblastoma gene product.

By using in vitro binding assays and the yeast two-hybrid system, we have found that a full-length rat Cdc37-related protein (RCdc37) could associate specifically with the retinoblastoma susceptibility gene product (pRB). A series of GST-RCdc37 deletion mutants was constructed to define the amino acid sequence required for the interaction with pRB. A GST-RCdc37 (-20 approximately 229) possessed an activity to associate with pRB, whereas GST-RCdc37 (-20 approximately 165) lost its activity, indicating that the amino acid sequence between 166 and 229 of RCdc37 was essential for the association with pRB. Interestingly, there exists a highly conserved pRB-binding motif (LXCXE; X = any amino acid) that is essential for pRB binding of SV40 large T antigen, E1A, and E7 proteins. A similar experiment using a pRB deletion mutant revealed that the carboxy-terminal portion of pRB was required for binding to RCdc37.