The role of ZRF1 in epigenetic control of transcription and tumor progression.
Final Report Abstract
The focus of the DFG-funded fellowship was the analysis of molecular mechanisms of epigenetic gene silencing and its impact on transcription and cell differentiation. When I joined the laboratory of Luciano Di Croce, significant progress had been made regarding the analysis of ZRF1 function in epigenetic control of transcriptional regulation, which led to publication of the results in Nature in 2010. In this article, it was shown that Polycomb repressed genes are activated by the recruitment of ZRF to the promoter and subsequent displacement of the PRC1 complex. We followed up on the link between the repressive function of the PRC2 complex and activating histone modificatons, specifically methylated lysine 36 on histone 3, since we had identified Phf19 as a novel subunit of the PRC2 complex that interacts with this “active” histone modification. Within this project, we were able to generate previously unavailable human and mouse-specific polyclonal antibodies against Phf19. This was a challenging task due to the high sequence conservation between members of the protein family. In order to ensure specificity of the antibodies, only certain - less conserved regions - were suitable as antigens. Moreover, we characterized Phf19 function in mouse embryonic stem cells, where we found it to be important to maintain ES cell pluripotency. This function was assigned to its role in regulating PRC2 enzymatic activity, as loss of Phf19 leads to loss of PRC2-mediated H3K27 methylation. This role was further demonstrated by the Genome-wide Chromatin binding profile of Phf19 in ES cells, which showed a very high overlap with PRC2 occupancy on the promoters of repressed genes. In line with this, Genome-wide mRNA expression analysis of ES cells interfered for Phf19 showed a deregulation of the normally repressed genes and loss of pluripotency. Finally, we carried out a detailed biochemical and biophysical characterization of the novel Phf19-Tudor/H3K36me interaction. Within the project we were able to establish collaborations with top research institutions in Germany (EMBL Heidelberg, Laboratory of Teresa Carlomagno, Audrone Lapinaite) and the USA (Stanford University, Laboratory of Or Gozani, Gloria Mas Martin). At the CRG, a PhD student was hired to study the role of Phf19 in tumor formation. Her first results are very promising and point to a role of Phf19 in regulation the Ink4/ARF locus in cancer cells. Since we were able to solve the solution structure of Phf19-Tudor domain in complex with the H3K36me3 peptide the CRG is evaluating if the Phf19-Tudor domain can be used as a drug target in the context of melanoma and glioma, two typed in cancers in which Phf19 is over-expressed.
Publications
- Setting and resetting of epigenetic marks in malignant transformation and development. Bioessays. 2010 Aug;32(8):669-79
Richly H, Lange M, Simboeck E, Di Croce L
- Transcriptional activation of polycomb-repressed genes by ZRF1. Nature. 2010 Dec 23;468(7327):1124-8
Richly H, Rocha-Viegas L, Ribeiro JD, Demajo S, Gundem G, Lopez-Bigas N, Nakagawa T, Rospert S, Ito T, Di Croce L
- Combinatorial assembly and function of chromatin regulatory complexes. Epigenomics October 2011, Vol. 3, No. 5, Pages 567-580
Martin Lange, Santiago Demajo, Payal Jain & Luciano Di Croce
