Cloning of a new member of the retinoblastoma gene family (pRb2) which binds to the E1A transforming domain.

The product of the retinoblastoma tumor suppressor gene (pRb) and p107 share a high degree of structural homology in the pocket region, which is thought to play a primary role in the function of these proteins. It is conceivable that there exists a larger family of cellular proteins containing this pocket region. In this communication, we report cloning of a new human cDNA encoding a polypeptide that shows a high level of identity with pRb and p107 and possesses a pocket region. We have named it pRb2. From the deduced amino acid sequence, pRb2 has a predicted molecular weight of approximately 120 kD and its in vitro translated product binds to the adenovirus E1A protein. Due to its size, pRb2 may correspond to p130, which has previously been shown by us to interact with the transforming region of E1A in in vivo studies. Interestingly, pRb2 fails to bind an E1A mutant in the transforming domain 2 suggesting that pRb2 is involved in the transforming capacity of E1A.