Abstract 2010: Charactering the interactomes of the Myc family of oncogenes
Authors: Resetca Diana , Dingar Dharmesh , Kalkat Manpreet , Raught Brian , Penn Linda Z. 
Published: July 2016

Abstract
The Myc family of transcription factors, c-Myc, N-Myc and L-Myc, are known to be deregulated in a large variety of cancers. Mechanisms responsible for the deregulation of the activity of Myc family members in cancer are not well understood. A number of protein-protein interactions and post-translational modifications have been suggested to promote the oncogenic activity of Myc. Traditional biochemical approaches have not been successful at mapping the interactors of Myc family members due to their tight association with chromatin and the labile nature of Myc proteins. Mapping the protein-protein interactions that support the aberrant activity of Myc family of oncoproteins in cancer cells is of high interest, particularly in a more natural context in xenograft models in vivo.
A new mass spectrometry-based technique, BioID-MS, which relies on proximity-based biotin labeling, has recently emerged as a key advance for the characterization of hard-to-detect protein-protein interactions in living cells. Herein, we are reporting a new application of the BioID-MS technique for the characterization of c-Myc interactors in human cell line in vivo, in mouse tumor xenografts. Using the in vivo BioID assay, we were able to identify more than 30 known and validated c-Myc interactors, some of which include the components of the STAGA complex and SWI/SNF chromatin remodelling complex. We were further able to identify more than 100 novel high-confidence c-Myc interactors, which include components of the DNA repair and replication machinery, general transcription and elongation factors, and the co-regulator of transcription-like DNA helicase protein chromodomain 8 (CHD8). Using ENCODE ChIP-seq datasets we were able to map some of the high-confidence interactors to coincident binding sites with c-Myc throughout the genome. This provided further credibility that the newly identified putative interactors could co-occupy sites on chromatin with c-Myc and could be functionally important for activity. Furthermore, we validated the Myc-CHD8 interaction using a number of approaches, including yeast two hybrid and proximity-based ligation assays.
These findings suggest that the BioID-MS technique can be used to extend the mapping of the Myc interactome and contribute to a greater understanding of Myc regulation by protein-protein interactions. Furthermore, we are currently in the process of employing this technique to map the interactomes of two other Myc family members, N-Myc and L-Myc. We are interested in identifying common interactors of the Myc family members that contribute to their oncogenic activity, validate them, and explore whether these interactors could be potential therapeutic targets in cancers with deregulated Myc activity.
Citation Format: Diana Resetca, Dharmesh Dingar, Manpreet Kalkat, Brian Raught, Linda Z. Penn. Charactering the interactomes of the Myc family of oncogenes. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2010.