Abstract 2950: Regulation of the functional interface between nucleotide excision repair and transcription by MITF modulates melanoma growth
Authors: Seoane Marcos , Raluy Laia Pagerols , Kaufmann Karoline , Strauss Julia , Dierck Kevin , Thomale Jüergen , Brandner Johanna M. , Schumacher Udo , Nollau Peter , Wild Peter J. , Zimmermann Martin , Du Jinyan , Fisher David E. , Horstmann Martin A. 
Published: May 2015

Nucleotide excision repair (NER) is an essential instrument to maintain genomic stability in eukaryotes especially towards ultraviolet radiation (UVR). There is profound knowledge of the mechanistic execution of NER, however its regulation is not well understood. Here we provide evidence that the lineage-dependent oncogene MITF regulates the functional interface between NER and transcription through transactivation of XPG and GTF2H1, which constitute core elements of the NER and general transcription factor machineries, respectively.

For this purpose, flow cytometry and microscopy fluorescence assays were applied to evaluate the temporal repair kinetics of DNA lesions after UVR in the presence and upon depletion of MITF in human primary melanocytes and several melanoma cell lines. Moreover, ChIP and luciferase reporter assays were performed to show the in vivo occupancy and a MITF dependent transactivation of the XPG and GTF2H1 promoters. Transcriptome as well as tissue microarrays (TMA) analysis were used to demonstrate the relationship between MITF and TFIIH. Finally, in vivo experiments were performed utilizing a subcutaneous xenograft tumor model in SCID mice to confirm our hypothesis.

Our results showed that the NER/TFIIH complex is controlled by MITF in the presence and absence of UVR mediated genotoxic attack resulting in nucleotide repair deficiency and breakdown of global transcription upon MITF depletion. Importantly, in primary human melanoma the TFIIH subunit GTF2H1, which is involved in NER and RNA transcription, is linked to MITF abundance and prognostic melanoma stage. Moreover, RNA-interference mediated repression of GTF2H1 led to a significant reduction in tumor formation in a melanoma xenograft model.

Collectively, these results describe an unanticipated role of MITF in the regulation of intimately linked NER and transcription machineries in the melanocytic lineage, which is preserved upon transformation into melanoma. Through its control of the NER/TFIIH complex MITF might coordinately regulate repair and transcription processes, thereby optimizing the rapid resumption of transcriptional activity after completion of strand repair, which is vitally important for cellular survival. The very same mechanism may drive the genesis of melanoma and its progression in the context of aberrant transcriptional activity of MITF due to SUMOylation defective germline mutation or genomic amplification.

Citation Format: Marcos Seoane, Laia Pagerols Raluy, Karoline Kaufmann, Julia Strauss, Kevin Dierck, Jüergen Thomale, Johanna M. Brandner, Udo Schumacher, Peter Nollau, Peter J. Wild, Martin Zimmermann, Jinyan Du, David E. Fisher, Martin A. Horstmann. Regulation of the functional interface between nucleotide excision repair and transcription by MITF modulates melanoma growth. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2950. doi:10.1158/1538-7445.AM2014-2950