YY1 promotes colorectal cancer proliferation through the miR-526b-3p/E2F1 axis

We previously reported that E2F1 expression is up-regulated and positively correlated with the malignant phenotypes of colorectal cancer (CRC). However, the underlying mechanisms leading to the aberrant up-regulation of E2F1 in CRC have not been clarified. In this study, we observed that miR-526b-3p directly targets the 3'UTR of E2f1 mRNA, leading to reduced E2F1 expression. Overexpression of miR-526b-3p inhibited the proliferation of CRC cells by decreasing the level of E2F1. We also found that the Ying Yang 1 (YY1)-dependent transcriptional suppression of miR-526b-3p is responsible for the up-regulation of E2F1 in CRC, in which YY1 binds to the promoter of miR-526b gene and recruits histone deacetylase (HDAC). Knockdown of YY1 led to cell cycle arrest and diminished colony formation in CRC cells partly through relieving the miR-526b-3p suppression. Clinical analysis showed that YY1 and E2F1 were negatively correlated with miR-526b-3p in CRC tissues. Moreover, a high level of YY1 and E2F1, or a low level of miR-526b-3p, predicted poor survival of CRC patients. In conclusion, our findings highlight the dysregulation of the YY1/miR-526b-3p/E2F1 axis in CRC development, implicating a novel regulatory pathway for E2F1 as a potential therapeutic target in CRC.