Identification and cloning of the cDNA of a Rb-associated protein RAP140a

Rb exerts important physiological functions in cell-cycle control, gene expression, cell differentiation, apoptosis, development and tumorigenesis by interacting with many cellular proteins. Using human partial Rb as bait, we screened a human fetal brain cDNA library through yeast two-hybrid system and obtained six novel cDNA fragments. Among them, one cDNA fragment corresponds to two different transcripts, 7 kb and 9 kb in Northern blot analysis. These two transcripts showed uniform distribution in various human tissues. We cloned the full-length cDNA of a 7.2 kb transcript through three times PCR amplifications. It was named RAP140a and predicted to encode a 1 233 amino acids hydrophilic protein. RAP140a was mapped to chromosome 3p13-p14.1. RAP140a may be functionally related to the intracellular translocation of Rb or other proteins.