Retinoblastoma Binding Protein 5 (RBBP5)

Retinoblastoma-binding protein 5 is a ubiquitously expressed nuclear protein and belongs to a highly conserved subfamily of WD-repeat proteins. It is found among several proteins that bind directly to retinoblastoma protein, which regulates cell proliferation. The encoded protein interacts preferentially with the underphosphorylated retinoblastoma protein via the E1A-binding pocket B.The total nucleotide sequence of 1 of these clones, RBBP5, which the aurhors designated RBQ3, was found to encode a protein of 66 kD localized in the nucleus. RBBP5 protein preferentially binds to underphosphorylated RB protein. The region used for binding to this protein was mapped to the E1A-binding pocket B of pRB, which has sequence similarity to the general transcription factor TFIIB .