Poster presentation, P35

Official XXIst International Pigment Cell Conference website - 21-24 Sept 2011, Bordeaux - France | updated: September 04 2011

Identification and characterisation of the MITF-interactome

The transcription factor MITF plays a pivotal role in melanoma. We previously performed profiling of MITF genomic occupancy by ChIP-seq in human 501Mel cells and identified MITF regulated genes by RNA-seq following siRNA-mediated MITF knockdown. This approach showed that loss of MITF leads to both down- and up-regulation of target genes involved in DNA replication, repair and mitosis, invasion and metastasis, indicating that it acts as a transcriptional activator or repressor in a promoter-specific manner. The identification of MITF partners proteins, and characterisation of their role in MITF-mediated gene regulatory networks may explain how it exerts this “dual function”. We have generated 501 mel cells expressing Flag-HA tagged MITF and performed tandem affinity purification followed by mass-spectrometry of both the soluble nuclear and chromatin associated MITF fractions. Using this approach, we identified many of known partners (for example b-catenin and subunits of the BRG1 chromatin remodeling complex). We also show that MITF forms heterodimers with TFE3, TFEB and TFEC in melanoma cells suggesting that MITF does not occupy all of its genomic sites as a homodimer. In addition, we identify a set of other factors that may potentially act as transcription co-activators and repressors. Interestingly, we identified novel potential MITF-interactors that are directly involved in the DNA replication and repair processes. This suggests that MITF may regulate DNA repair and genome stability not only through its ability to regulate the expression of genes involved in this processes as we previously reported, but also in a much more direct manner.

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