Identification of interferon regulatory factor 4 (IRF4)-interacting proteins in melanoma cell lines

IRF4 is a member of interferon regulatory factor family of transcription factors. Previously, IRF4 was shown to have regulatory roles in immune cells and B-cell malignancies. In addition, IRF4 was recently shown to be expressed in cells other than immune related cells; such as adipocytes and melanocytes. Its expression in melanocytes and certain melanoma cell lines guided us to investigate the role of IRF4 in melanoma. Proteins interact with other proteins in the cells to function properly. There are many identified interaction partners of IRF4 in immune cells and especially the interaction of IRF4 with some members of ETS family transcription factors was observed to have a critical role in B-cell malignancies. However, interaction partners of IRF4 are not identified in melanoma cell lines; identification of these proteins might shed a light on the role of IRF4 in melanoma cell progression. For this purpose, we used Tandem affinity purification (TAP) and BioID methods to identify the interaction partners of IRF4. The candidate IRF4-interacting proteins identified with mass spectrometry data from TAP and BioID, are mostly involved in pre-mRNA processing and splicing, suggesting a role for IRF4 in these processes; yet further studies should be conducted to conclude the role of IRF4 in pre-mRNA processing and splicing. Two of the proteins, obtained from the mass spectrometry data of TAP and BioID, were studied further to validate their interaction with IRF4 and one of them was shown to interact with IRF4 in SKMEL28 melanoma cell line via other methods in addition to TAP and BioID. This transcription factor is a novel interaction partner of IRF4, which was not shown to be correlated with IRF4 in other studies.