Retinoblastoma-like protein 1, also named RBL1, p107, is a member of E1A-binding proteins, which contains a A/B pocket, or pRb. Via this structure, RBL1 can bind to viral oncoproteins and other perteins containing LXCXE motif. It regulates cell proliferation via phosphorylation-sensitive interactions with E2F transcription factors and other proteins. Key regulator of entry into cell division. Directly involved in heterochromatin formation by maintaining overall chromatin structure and, in particular, that of constitutive heterochromatin by stabilizing histone methylation. Recruits and targets histone methyltransferases SUV420H1 and SUV420H2, leading to epigenetic transcriptional repression.(uniprot). It has been reported there are two transcirpts variants of RBL1, which encode a 119-kd protein and a 68-kd protein(PMID:7490090).