The CARM1-p300-c-Myc-Max (CPCM) transcriptional complex regulates the expression of CUL4A/4B and affects the stability of CRL4 E3 ligases in colorectal cancer

Abstract

The transcription factor c-Myc and two cullin family members CUL4A/4B function as oncogenes in colorectal cancer. Our recent publication reveals that c-Myc specifically activates the expression of CUL4A/4B through binding to their promoters. However, the underlying mechanism of how c-Myc actions in this process is still unknown. Using mass spectrometry and immunoprecipitation assays, we identified c-Myc formed a transcriptional complex with its partner Max (Myc-associated factor X), a histone acetyltransferase p300 and a coactivator associated arginine methyltransferase 1 (CARM1) in the present study. Knockdown or overexpression of the components of CARM1-p300-c-Myc-Max (CPCM) complex resulted in a decrease or increase of CUL4A/4B levels, respectively. Individual knockdown or inhibition of CPCM components decreased cell proliferation, colony formation, and cell invasion. Biochemically, knockdown or inhibition of CPCM components decreased their occupancies on the promoters of CUL4A/4B and resulted in their downregulation. Importantly, inhibition of CPCM components also caused a decrease of CRL4 E3 ligase activities and eventually led to an accumulation of ST7 (suppression of tumorigenicity 7), the specific substrate of CRL4 E3 ligases in colorectal cancer. Moreover, the in vivo tumor formation results indicated that knockdown or inhibition of CPCM components significantly decreased the tumor volumes. Together, our results suggest that the CPCM complex mediates explicitly the expression of CUL4A/4B, and thus affects the stability of CRL4 E3 ligases and the ubiquitination of ST7. These results provide more options by targeting the CPCM components to inhibit tumor growth in the therapy of colorectal cancer.

Targeting Myc Interacting Proteins as a Winding Path in Cancer Therapy

“…Six lysine residues in Myc are direct substrates of p300, and acetylated Myc could interact with promoter binding factors as Miz-1 effectively (Zhang et al, 2005). A recent study reported that p300 binds to c-Myc N-terminus and recruit co-activator-associated arginine methyltransferase 1 (CARM1), in which CARM1-p300-c-Myc-Max (CPCM) transcriptional complex controls the transcription of CUL4A/4B (Lu et al, 2020 indicating that this function is independent of TRRAP (Vervoorts et al, 2003).…”

IL-18-Mediated SLC7A5 Overexpression Enhances Osteogenic Differentiation of Human Bone Marrow Mesenchymal Stem Cells via the c-MYC Pathway

“…The c-MYC pathway also plays a key role in the maintenance of T cell function and metabolic reprogramming and is independent of the mTOR pathway. The physiological condition, in terms of the transcription levels of c-MYC, reflects tissue and cell growth status; tissues with high proliferation rates have high c-MYC transcription levels (Lu et al, 2020). Several studies have demonstrated that many types of tumors are characterized by high c-MYC expression levels; however, in the absence of other mutations, c-MYC overexpression alone is not sufficient for tumorigenic transformation.…”

Two naturally derived small molecules disrupt the sineoculis homeobox homolog 1–eyes absent homolog 1 (SIX1–EYA1) interaction to inhibit colorectal cancer cell growth

“…[ 2 ] The sources and growth conditions of seven CRC cell lines including HT29, HT55, HCT-15, HCT-116, HCA-24, SW620, and T84 were the same as described previously. [ 18 ] For short hairpin RNA (shRNA) transfection, two independent MISSION shRNA lentiviral transduction particles of SIX1 (#TRCN0000015235 and #TRCN0000015237) and EYA1 (#TRCN0000303462 and #TRCN0000315624) were purchased from Sigma-Aldrich (St. Louis, MO, USA). These particles and pLKO.1-puro (Control) were individually transfected with FuGene 6 (Roche Diagnostics Corp., Indianapolis, IN, USA, #E2691) into cells following the manufacturer's protocol.…”

“…The ChIP assay was carried out as described previously. [ 18 ] To elucidate, cells (1 × 10 8 ) were cross-linked with 1% formaldehyde for 12 min, followed by quenching with 0.125 mmol/L glycine for 10 min. After rinsing twice with PBS buffer, cells were sonicated 15 × 30 s on ice in 4 mL lysis buffer provided by the Millipore ChIP Assay Kit (Millipore, Burlington, MA, USA, #17295).…”