2r7g

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] [E1A_ADE05] E1A protein has both transforming and trans-activating activities. Plays a role in viral genome replication by driving entry of quiescent cells into the cell cycle. Disrupts the function of host retinoblastoma protein RB1/pRb and isoform early E1A 26 kDa protein stabilizes TP53, which are key regulators of the cell cycle. Induces the disassembly of the E2F1 transcription factors from RB1 by direct competition for the same binding site on RB1, with subsequent transcriptional activation of E2F1-regulated S-phase genes. Inactivation of the ability of RB1 to arrest the cell cycle is critical for cellular transformation, uncontrolled cellular growth and proliferation induced by viral infection. Stimulation of progression from G1 to S phase allows the virus to efficiently use the cellular DNA replicating machinery to achieve viral genome replication. Interaction with RBX1 and CUL1 inhibits ubiquitination of the proteins targeted by SCF(FBW7) ubiquitin ligase complex, and may be linked to unregulated host cell proliferation. The tumorigenesis-restraining activity of E1A may be related to the disruption of the host CtBP-CtIP complex through the CtBP binding motif.^{[15] [16] [17] [18]}

Evolutionary Conservation

Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.

References

1. ↑ 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
2. ↑ 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
3. ↑ 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
4. ↑ 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
5. ↑ 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
6. ↑ 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
7. ↑ 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
8. ↑ 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
9. ↑ 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
10. ↑ 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
11. ↑ 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
12. ↑ 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
13. ↑ 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
14. ↑ Ren S, Rollins BJ. Cyclin C/cdk3 promotes Rb-dependent G0 exit. Cell. 2004 Apr 16;117(2):239-51. PMID:15084261
15. ↑ Nakajima T, Morita K, Tsunoda H, Imajoh-Ohmi S, Tanaka H, Yasuda H, Oda K. Stabilization of p53 by adenovirus E1A occurs through its amino-terminal region by modification of the ubiquitin-proteasome pathway. J Biol Chem. 1998 Aug 7;273(32):20036-45. PMID:9685342
16. ↑ Ledl A, Schmidt D, Muller S. Viral oncoproteins E1A and E7 and cellular LxCxE proteins repress SUMO modification of the retinoblastoma tumor suppressor. Oncogene. 2005 May 26;24(23):3810-8. PMID:15806172 doi:10.1038/sj.onc.1208539
17. ↑ Isobe T, Hattori T, Kitagawa K, Uchida C, Kotake Y, Kosugi I, Oda T, Kitagawa M. Adenovirus E1A inhibits SCF(Fbw7) ubiquitin ligase. J Biol Chem. 2009 Oct 9;284(41):27766-79. Epub 2009 Aug 13. PMID:19679664 doi:M109.006809
18. ↑ Yousef AF, Fonseca GJ, Pelka P, Ablack JN, Walsh C, Dick FA, Bazett-Jones DP, Shaw GS, Mymryk JS. Identification of a molecular recognition feature in the E1A oncoprotein that binds the SUMO conjugase UBC9 and likely interferes with polySUMOylation. Oncogene. 2010 Aug 19;29(33):4693-704. doi: 10.1038/onc.2010.226. Epub 2010 Jun, 14. PMID:20543865 doi:10.1038/onc.2010.226
19. ↑ Liu X, Marmorstein R. Structure of the retinoblastoma protein bound to adenovirus E1A reveals the molecular basis for viral oncoprotein inactivation of a tumor suppressor. Genes Dev. 2007 Nov 1;21(21):2711-6. PMID:17974914 doi:21/21/2711