RBL1 siRNA – Retinoblastoma-Like Protein 1 Isoform a (Human)

The protein encoded by this gene is similar in sequence and possibly function to the product of the retinoblastoma 1 (RB1) gene. The RB1 gene product is a tumor suppressor protein that appears to be involved in cell cycle regulation, as it is phosphorylated in the S to M phase transition and is dephosphorylated in the G1 phase of the cell cycle. Both the RB1 protein and the product of this gene can form a complex with adenovirus E1A protein and SV40 large T-antigen, with the SV40 large T-antigen binding only to the unphosphorylated form of each protein. In addition, both proteins can inhibit the transcription of cell cycle genes containing E2F binding sites in their promoters. Due to the sequence and biochemical similarities with the RB1 protein, it is thought that the protein encoded by this gene may also be a tumor suppressor. Two transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Jul 2008]

Rb-like 1: 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. Controls histone H4 'Lys-20' trimethylation. Probably acts as a transcription repressor by recruiting chromatin-modifying enzymes to promoters. Potent inhibitor of E2F-mediated trans-activation. Forms a complex with adenovirus E1A and with SV40 large T antigen. May bind and modulate functionally certain cellular proteins with which T and E1A compete for pocket binding. May act as a tumor suppressor. Belongs to the retinoblastoma protein (RB) family. 2 isoforms of the human protein are produced by alternative splicing.

Protein type: Transcription, coactivator/corepressor; Tumor suppressor

Chromosomal Location of Human Ortholog: 20q11.2

Cellular Component: nucleoplasm; transcription factor complex; nucleus

Molecular Function: protein binding; transcription factor binding

Biological Process: transcription initiation from RNA polymerase II promoter; viral reproduction; transcription, DNA-dependent; regulation of cell cycle; transforming growth factor beta receptor signaling pathway; positive regulation of transcription from RNA polymerase II promoter; gene expression; regulation of lipid kinase activity; chromatin modification; mitotic cell cycle; negative regulation of transcription from RNA polymerase II promoter