The Retinoblastoma family consists of three genes, RB, p107, and Rb2/p130, all fundamental
in the control of important cellular phenomena, such as cell cycle, differentiation,
and apoptosis. The “founder” and the most investigated gene of the family is RB,
which is considered the prototype for the tumor suppressor genes (1,2). The other two
genes, p107 and Rb2/p130, and the proteins they code for, p107 and pRb2/p130, respectively,
clearly reflect a high degree of structural and functional similarity to the RB
gene product, pRb (3,4). The RB family proteins were disclosed initially by investigators
working on viral oncoproteins. In particular, a set of proteins associated with the
Adenovirus 5 E1A oncoprotein was identified, and the bands representing the most
abundant ones were named p60, p105, p107, p130, and p300, in keeping with their apparent
molecular mass, as determined by SDS-PAGE (5). The subsequent characterization
of these proteins identified p105 as the product of the RB gene (6). Later, genes
encoding p107 (7,8) and pRb2/p130 (9–11) were cloned using different strategies