O-GlcNAcylation promotes colorectal cancer progression by regulating protein stability and potential catcinogenic function of DDX5.

The RNA helicase p68 (DDX5), a key player in RNA metabolism, belongs to the DEAD box family and is involved in the development of colorectal cancer. Here, we found both DDX5 and O-GlcNAcylation are up-regulated in colorectal cancer. In addition, DDX5 protein level is significantly positively correlated with the expression of O-GlcNAcylation. Although it was known DDX5 protein could be regulated by post-translational modification (PTM), how O-GlcNAcylation modification regulated of DDX5 remains unclear. Here we show that DDX5 interacts directly with OGT in the SW480 cell line, which is the only known enzyme that catalyses O-GlcNAcylation in humans. Meanwhile, O-GlcNAcylation could promote DDX5 protein stability. The OGT-DDX5 axis affects colorectal cancer progression mainly by regulating activation of the AKT/mTOR signalling pathway. Taken together, these results indicated that OGT-mediated O-GlcNAcylation stabilizes DDX5, promoting activation of the AKT/mTOR signalling pathway, thus accelerating colorectal cancer progression. This study not only reveals the novel functional of O-GlcNAcylation in regulating DDX5, but also reveals the carcinogenic effect of the OGT-DDX5 axis in colorectal cancer.