Mass spectrometry-based proteomic capture of proteins bound to the MACC1 promoter in colon cancer.

MACC1 (metastasis associated in colon cancer 1) is a key driver that induces metastasis in colon cancer. However, the mechanisms by which MACC1 expression is transcriptionally regulated and the factors enriched at the MACC1 promoter remain largely unknown. The binding of proteins to specific DNA sites in the genome is a major determinant of genomic maintenance and the regulation of specific genes. The study herein utilized two methods to study the binding proteins of the MACC1 promoter region in colon cancer. Specifically, we adopted CRISPR-based chromatin affinity purification with mass spectrometry (CRISPR-ChAP-MS) and a biotin-streptavidin pulldown assay coupled with MS to identify the specific proteome bound to the MACC1 promoter in two colon cell lines with different metastatic potential. A total of 24 proteins were identified by CRISPR-ChAP-MS as binding to the MACC1 promoter, among which c-JUN was validated by ChIP-PCR. A total of 739 binding protein candidates were identified by biotin-streptavidin pulldown assays coupled with MS, of which HNF4G and PAX6 were validated and compared for their binding to the same promoter sites in the two cell lines. Our studies suggest distinctive proteomic factors associated with the MACC1 promoter in colon cells with different metastatic potential. The dynamic regulatory factors accumulated at the promoter of MACC1 may provide novel insights into the regulatory mechanisms of MACC1 transcription.