The pocket protein family consists of three structurally and functionally related proteins, Rb (retinoblastoma), p107, and p130. This family of tumor suppressors function to regulate important cellular transcription factors, such as the E2F family. The E2F proteins regulate the expression of genes whose products are important for cell cycle progression. The inactivation Rb is catalyzed by CDK phosphorylation thereby releasing E2F during the G1-S phase cellular progression. Unchecked inactivat