Isolation and chromosomal localization of a new human retinoblastoma binding protein 2 homologue 1a ( RBBP2H1A )

Using a Not I linking clone NR-025 as a probe, we isolated a novel putative member of the RB binding protein family, namely a human retinoblastoma binding protein 2 homologue ( RBBP2H1A ). The maximal open reading frame encodes a protein of 1681 amino acids. Homology analysis indicated that the predicted product has an overall 56% amino acid identity to RBBP2, which plays an important role in RB tumor suppressor regulation. Many extended regions are 100% identical in amino acids sequences. The degree of nucleotide identity is lower. The structure prediction analysis identified three DNA-binding zinc finger domains and two bipartite nuclear localization signals. Northern expression analysis revealed expression in all tissues; however, the level of expression significantly varied between tissues. The highest level of expression was detected in testis and the lowest in skeletal muscle. The mRNA sizes corresponding to two major products are around 6kb and 7kb. Using fluorescence in situ hybridization, we mapped the gene to chromosomal band 1q32.1.