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Crystal structure of the retinoblastoma tumour suppressor protein bound to E2F peptide
Structural highlights
DiseaseRB_HUMAN Defects in RB1 are the cause of childhood cancer retinoblastoma (RB) [MIM:180200. RB is a 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.[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] Defects in RB1 are a cause of susceptibility to bladder 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. They 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. Defects in RB1 are a cause of osteogenic sarcoma (OSRC) [MIM:259500. FunctionRB_HUMAN 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.[14] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe retinoblastoma tumor suppressor protein (pRb) regulates the cell cycle, facilitates differentiation, and restrains apoptosis. Furthermore, dysfunctional pRb is thought to be involved in the development of most human malignancies. Many of the functions of pRb are mediated by its regulation of the E2F transcription factors. To understand the structural basis for this regulation, we have determined the crystal structure of a fragment of E2F in complex with the pocket domain of the tumor suppressor protein. The pRb pocket, comprising the A and B cyclin-like domains, is the major focus of tumourigenic mutations in the protein. The fragment of E2F used in our structural studies, residues 409-426 of E2F-1, represents the core of the pRb-binding region of the transcription factor. The structure shows that E2F binds at the interface of the A and B domains of the pocket making extensive interactions with conserved residues from both. We show by solution studies that a second site, probably contained within the "marked box" region of E2F, is responsible for additional interactions with the pRb pocket but is insufficient for complex formation on its own. In addition, we show that the interaction of the core binding fragment of E2F with pRb is inhibited by phosphorylation of the tumor suppressor protein by CDK2cyclin DE. Finally, our data reveal that the tight binding of the human papillomavirus E7 oncoprotein to pRb prevents subsequent interactions with the marked box region of E2F but not with its core binding region. Crystal structure of the retinoblastoma tumor suppressor protein bound to E2F and the molecular basis of its regulation.,Xiao B, Spencer J, Clements A, Ali-Khan N, Mittnacht S, Broceno C, Burghammer M, Perrakis A, Marmorstein R, Gamblin SJ Proc Natl Acad Sci U S A. 2003 Mar 4;100(5):2363-8. Epub 2003 Feb 21. PMID:12598654[15] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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