The bromodomain protein TRIM28 controls the balance between growth and invasiveness in melanoma

Melanoma tumors are highly metastatic partly due to the ability of melanoma cells to transition between invasive and proliferative states, however, the mechanisms underlying this plasticity are still not fully understood. To identify new epigenetic regulators of melanoma plasticity, we combined data mining, tumor models, proximity proteomics, and CUT&RUN-sequencing. We focused on the druggable family of bromodomain epigenetic readers, and identified TRIM28 as a new regulator of melanoma plasticity. We found that TRIM28 promotes the expression of pro-invasive genes, and that TRIM28 controls the balance between invasiveness and growth of melanoma cells. We demonstrate that TRIM28 acts via the transcription factor JUNB, that directly regulates the expression of pro-invasive and pro-growth genes. Mechanistically, TRIM28 controls the expression of JUNB by negatively regulating its transcriptional elongation by RNA polymerase II. In conclusion, our results demonstrate that a TRIM28-JUNB axis controls the balance between invasiveness and growth in melanoma tumors and suggests that the bromodomain protein TRIM28 could be targeted to reduce tumor spread. Overall design: A375 melanoma cells were transduced with pBABE empty vector, pBABE-FOSL1 or pBABE-JUNB followed by RNA-seq to determine gene expression levels. To determine the genome binding/occupancy profiles of TRIM28 and RNA polymerase II in A375 cells we used CUT&RUN.