| Structural highlights
Disease
[RB_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].
Function
[RB_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]
Publication Abstract from PubMed
Cyclin-dependent kinase (Cdk) phosphorylation of the Retinoblastoma protein (Rb) drives cell proliferation through inhibition of Rb complexes with E2F transcription factors and other regulatory proteins. We present the first structures of phosphorylated Rb that reveal the mechanism of its inactivation. S608 phosphorylation orders a flexible "pocket" domain loop such that it mimics and directly blocks E2F transactivation domain (E2F(TD)) binding. T373 phosphorylation induces a global conformational change that associates the pocket and N-terminal domains (RbN). This first multidomain Rb structure demonstrates a novel role for RbN in allosterically inhibiting the E2F(TD)-pocket association and protein binding to the pocket "LxCxE" site. Together, these structures detail the regulatory mechanism for a canonical growth-repressive complex and provide a novel example of how multisite Cdk phosphorylation induces diverse structural changes to influence cell cycle signaling.
Structures of inactive retinoblastoma protein reveal multiple mechanisms for cell cycle control.,Burke JR, Hura GL, Rubin SM Genes Dev. 2012 May 8. PMID:22569856[15]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Yandell DW, Campbell TA, Dayton SH, Petersen R, Walton D, Little JB, McConkie-Rosell A, Buckley EG, Dryja TP. Oncogenic point mutations in the human retinoblastoma gene: their application to genetic counseling. N Engl J Med. 1989 Dec 21;321(25):1689-95. PMID:2594029
- ↑ Onadim Z, Hogg A, Baird PN, Cowell JK. Oncogenic point mutations in exon 20 of the RB1 gene in families showing incomplete penetrance and mild expression of the retinoblastoma phenotype. Proc Natl Acad Sci U S A. 1992 Jul 1;89(13):6177-81. PMID:1352883
- ↑ Hogg A, Bia B, Onadim Z, Cowell JK. Molecular mechanisms of oncogenic mutations in tumors from patients with bilateral and unilateral retinoblastoma. Proc Natl Acad Sci U S A. 1993 Aug 1;90(15):7351-5. PMID:8346255
- ↑ Cowell JK, Smith T, Bia B. Frequent constitutional C to T mutations in CGA-arginine codons in the RB1 gene produce premature stop codons in patients with bilateral (hereditary) retinoblastoma. Eur J Hum Genet. 1994;2(4):281-90. PMID:7704558
- ↑ Lohmann DR, Brandt B, Hopping W, Passarge E, Horsthemke B. Distinct RB1 gene mutations with low penetrance in hereditary retinoblastoma. Hum Genet. 1994 Oct;94(4):349-54. PMID:7927327
- ↑ Liu Z, Song Y, Bia B, Cowell JK. Germline mutations in the RB1 gene in patients with hereditary retinoblastoma. Genes Chromosomes Cancer. 1995 Dec;14(4):277-84. PMID:8605116
- ↑ Blanquet V, Turleau C, Gross-Morand MS, Senamaud-Beaufort C, Doz F, Besmond C. Spectrum of germline mutations in the RB1 gene: a study of 232 patients with hereditary and non hereditary retinoblastoma. Hum Mol Genet. 1995 Mar;4(3):383-8. PMID:7795591
- ↑ Van Orsouw NJ, Li D, van der Vlies P, Scheffer H, Eng C, Buys CH, Li FP, Vijg J. Mutational scanning of large genes by extensive PCR multiplexing and two-dimensional electrophoresis: application to the RB1 gene. Hum Mol Genet. 1996 Jun;5(6):755-61. PMID:8776589
- ↑ Lohmann DR, Gerick M, Brandt B, Oelschlager U, Lorenz B, Passarge E, Horsthemke B. Constitutional RB1-gene mutations in patients with isolated unilateral retinoblastoma. Am J Hum Genet. 1997 Aug;61(2):282-94. PMID:9311732 doi:10.1086/514845
- ↑ Mateu E, Sanchez F, Najera C, Beneyto M, Castell V, Hernandez M, Serra I, Prieto F. Genetics of retinoblastoma: a study. Cancer Genet Cytogenet. 1997 May;95(1):40-50. PMID:9140452
- ↑ Yilmaz S, Horsthemke B, Lohmann DR. Twelve novel RB1 gene mutations in patients with hereditary retinoblastoma. Mutations in brief no. 206. Online. Hum Mutat. 1998;12(6):434. PMID:10671068 doi:<434::AID-HUMU15>3.0.CO;2-A 10.1002/(SICI)1098-1004(1998)12:6<434::AID-HUMU15>3.0.CO;2-A
- ↑ Klutz M, Horsthemke B, Lohmann DR. RB1 gene mutations in peripheral blood DNA of patients with isolated unilateral retinoblastoma. Am J Hum Genet. 1999 Feb;64(2):667-8. PMID:9973307 doi:10.1086/302254
- ↑ Yu YS, Kim IJ, Ku JL, Park JG. Identification of four novel RB1 germline mutations in Korean retinoblastoma patients. Hum Mutat. 2001 Sep;18(3):252. PMID:11524739 doi:10.1002/humu.1184
- ↑ Ren S, Rollins BJ. Cyclin C/cdk3 promotes Rb-dependent G0 exit. Cell. 2004 Apr 16;117(2):239-51. PMID:15084261
- ↑ Burke JR, Hura GL, Rubin SM. Structures of inactive retinoblastoma protein reveal multiple mechanisms for cell cycle control. Genes Dev. 2012 May 8. PMID:22569856 doi:10.1101/gad.189837.112
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