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The Drosophila Retinoblastoma Binding Protein 6 Family Member Has Two Isoforms and Is Potentially Involved in Embryonic Patterning

School of Molecular & Cell Biology, University of the Witwatersrand, Johannesburg, South Africa Private Bag 3, WITS-2050 Johannesburg, South Africa
School of Life Sciences, University of KwaZulu-Natal (Pietermaritzburg campus); 3209 Scottsville, South Africa
Author to whom correspondence should be addressed.
Academic Editor: Bing Yan
Int. J. Mol. Sci. 2015, 16(5), 10242-10266;
Received: 21 January 2015 / Accepted: 13 March 2015 / Published: 6 May 2015
(This article belongs to the Section Biochemistry)
PDF [2336 KB, uploaded 6 May 2015]


The human retinoblastoma binding protein 6 (RBBP6) is implicated in esophageal, lung, hepatocellular and colon cancers. Furthermore, RBBP6 was identified as a strong marker for colon cancer prognosis and as a predisposing factor in familial myeloproliferative neoplasms. Functionally, the mammalian protein interacts with p53 and enhances the activity of Mdm2, the prototypical negative regulator of p53. However, since RBBP6 (known as PACT in mice) exists in multiple isoforms and pact−/ mice exhibit a more severe phenotype than mdm2−/ mutants, it must possess some Mdm2-independent functions. The function of the invertebrate homologue is poorly understood. This is complicated by the absence of the Mdm2 gene in both Drosophila and Caenorhabditis elegans. We have experimentally identified the promoter region of Snama, the Drosophila homologue, analyzed potential transcription factor binding sites and confirmed the existence of an additional isoform. Using band shift and co-immunoprecipitation assays combined with mass spectrometry, we found evidence that this gene may be regulated by, amongst others, DREF, which regulates hundreds of genes related to cell proliferation. The potential transcription factors for Snama fall into distinct functional groups, including anteroposterior embryonic patterning and nucleic acid metabolism. Significantly, previous work in mice shows that pact−/− induces an anteroposterior phenotype in embryos when rescued by simultaneous deletion of p53. Taken together, these observations indicate the significance of RBBP6 proteins in carcinogenesis and in developmental defects. View Full-Text
Keywords: retinoblastoma binding protein 6; RBBP6; SNAMA; p53; Rb; Mdm2 retinoblastoma binding protein 6; RBBP6; SNAMA; p53; Rb; Mdm2

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Hull, R.; Oosthuysen, B.; Cajee, U.-F.; Mokgohloa, L.; Nweke, E.; Antunes, R.J.; Coetzer, T.H.T.; Ntwasa, M. The Drosophila Retinoblastoma Binding Protein 6 Family Member Has Two Isoforms and Is Potentially Involved in Embryonic Patterning. Int. J. Mol. Sci. 2015, 16, 10242-10266.

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