Rb Recombinant Protein

The protein encoded by this gene is a negative regulator of the cell cycle and was the first tumor suppressor gene found. The encoded protein also stabilizes constitutive heterochromatin to maintain the overall chromatin structure. The active, hypophosphorylated form of the protein binds transcription factor E2F1. Defects in this gene are a cause of childhood cancer retinoblastoma (RB), bladder cancer, and osteogenic sarcoma. [provided by RefSeq, Jul 2008]

Function: Key regulator of entry into cell division that acts as a tumor suppressor. Promotes G0-G1 transition when phosphorylated by CDK3/cyclin-C. Acts as a transcription repressor of E2F1 target genes. The underphosphorylated, active form of RB1 interacts with E2F1 and represses its transcription activity, leading to cell cycle arrest. 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 SUV39H1, SUV420H1 and SUV420H2, leading to epigenetic transcriptional repression. Controls histone H4 'Lys-20' trimethylation. Inhibits the intrinsic kinase activity of TAF1. Mediates transcriptional repression by SMARCA4/BRG1 by recruiting a histone deacetylase (HDAC) complex to the c-FOS promoter. In resting neurons, transcription of the c-FOS promoter is inhibited by BRG1-dependent recruitment of a phospho-RB1-HDAC1 repressor complex. Upon calcium influx, RB1 is dephosphorylated by calcineurin, which leads to release of the repressor complex

By similarity. In case of viral infections, interactions with SV40 large T antigen, HPV E7 protein or adenovirus E1A protein induce the disassembly of RB1-E2F1 complex thereby disrupting RB1's activity. Ref.37

Subunit structure: Interacts with ATAD5. Interacts with PRMT2, CDK1 and CDK2

By similarity. The hypophosphorylated form interacts with and sequesters the E2F1 transcription factor. Interacts with heterodimeric E2F/DP transcription factor complexes containing TFDP1 and either E2F1, E2F3, E2F4 or E2F5, or TFDP2 and E2F4. The unphosphorylated form interacts with EID1, ARID3B, KDM5A, SUV39H1, MJD2A/JHDM3A and THOC1. Interacts with the N-terminal domain of TAF1. Interacts with SNW1, AATF, DNMT1, LIN9, LMNA, SUV420H1, SUV420H2, PELP1, UHRF2 and TMPO-alpha. May interact with NDC80. Interacts with GRIP1 and UBR4. Interacts with ARID4A and KDM5B. Interacts with E4F1 and LIMD1. Interacts with SMARCA4/BRG1 AND HDAC1

By similarity. Interacts with adenovirus E1A protein, HPV E7 protein and SV40 large T antigen. Interacts with PSMA3 and USP4. Interacts (when methylated at Lys-860) with L3MBTL1. Interacts with CHEK2; phosphorylates RB1. Interacts with human cytomegalovirus/HHV-5 protein UL123. Ref.13 Ref.16 Ref.19 Ref.20 Ref.21 Ref.22 Ref.23 Ref.25 Ref.26 Ref.27 Ref.28 Ref.29 Ref.30 Ref.31 Ref.32 Ref.33 Ref.34 Ref.35 Ref.36 Ref.38 Ref.39 Ref.41 Ref.42 Ref.43 Ref.44 Ref.45 Ref.46 Ref.47 Ref.53 Ref.57 Ref.63 Ref.65

Subcellular location: Nucleus Ref.54.

Tissue specificity: Expressed in the retina.

Domain: The Pocket domain binds to the threonine-phosphorylated domain C, thereby preventing interaction with heterodimeric E2F/DP transcription factor complexes.

Post-translational modification: Phosphorylated by CDK6 and CDK4, and subsequently by CDK2 at Ser-567 in G1, thereby releasing E2F1 which is then able to activate cell growth. Dephosphorylated at the late M phase. SV40 large T antigen, HPV E7 and adenovirus E1A bind to the underphosphorylated, active form of pRb. Phosphorylation at Thr-821 and Thr-826 promotes interaction between the C-terminal domain C and the Pocket domain, and thereby inhibits interactions with heterodimeric E2F/DP transcription factor complexes. Dephosphorylated at Ser-795 by calcineruin upon calcium stimulation. CDK3/cyclin-C-mediated phosphorylation at Ser-807 and Ser-811 is required for G0-G1 transition. Phosphorylated by CDK1 and CDK2 upon TGFB1-mediated apoptosis

By similarity. Ref.15 Ref.18 Ref.24 Ref.37 Ref.40 Ref.47 Ref.63N-terminus is methylated by METTL11A/NTM1

By similarity. Monomethylation at Lys-810 by SMYD2 enhances phosphorylation at Ser-807 and Ser-811, and promotes cell cycle progression. Monomethylation at Lys-860 by SMYD2 promotes interaction with L3MBTL1. Ref.53 Ref.59Acetylation at Lys-873 and Lys-874 regulates subcellular localization, at least during keratinocytes differentiation.

Involvement in disease: Childhood cancer retinoblastoma (RB) [MIM:180200]: Congenital malignant tumor that arises from the nuclear layers of the retina. It occurs in about 1:20'000 live births and represents about 2% of childhood malignancies. It is bilateral in about 30% of cases. Although most RB appear sporadically, about 20% are transmitted as an autosomal dominant trait with incomplete penetrance. The diagnosis is usually made before the age of 2 years when strabismus or a gray to yellow reflex from pupil ('cat eye') is investigated.Note: The disease is caused by mutations affecting the gene represented in this entry. Ref.66 Ref.67 Ref.68 Ref.69 Ref.70 Ref.71 Ref.72 Ref.73 Ref.74 Ref.75 Ref.76 Ref.77 Ref.78Bladder cancer (BLC) [MIM:109800]: A malignancy originating in tissues of the urinary bladder. It often presents with multiple tumors appearing at different times and at different sites in the bladder. Most bladder cancers are transitional cell carcinomas that begin in cells that normally make up the inner lining of the bladder. Other types of bladder cancer include squamous cell carcinoma (cancer that begins in thin, flat cells) and adenocarcinoma (cancer that begins in cells that make and release mucus and other fluids). Bladder cancer is a complex disorder with both genetic and environmental influences.Note: Disease susceptibility is associated with variations affecting the gene represented in this entry.Osteogenic sarcoma (OSRC) [MIM:259500]: A sarcoma originating in bone-forming cells, affecting the ends of long bones.Note: The disease is caused by mutations affecting the gene represented in this entry.

Sequence similarities: Belongs to the retinoblastoma protein (RB) family.