BackgroundEmerging studies have investigated circRNAs as significant regulation factors in multiple cancer progression. Nevertheless, the biological functions and underlying mechanisms of circRNAs in colorectal cancer progression remain unclear.MethodsA novel circRNA (circ-GALNT16) was identified by microarray and qRT-PCR. A series of phenotype experiments in vitro and vivo were performed to investigate the role of circ-GALNT16 in CRC. FISH, RNA pulldown assay, RIP assay, RNA sequencing, coimmunoprecipitation, and ChIP were constructed to explore the molecular mechanisms of circ-GALNT16 in colorectal cancer.ResultsCirc-GALNT16 was downregulated in colorectal cancer and negatively correlated with poor prognosis. Circ-GALNT16 suppressed the proliferation and metastasis ability of colorectal cancer in vitro and vivo. Mechanistically, circ-GALNT16 could bind to the KH3 domain of heterogeneous nuclear ribonucleoprotein K (hnRNPK), which resulted in the SUMOylation of hnRNPK. Additionally, circ-GALNT16 could enhance the hnRNPK-p53 complex by facilitating the SUMOylation of hnRNPK. Furthermore, RNA sequencing assay identified serpin family E member 1 as the target gene of circ-GALNT16 at the transcriptional level. Rescue assays revealed that circ-GALNT16 regulated the expression of Serpine1 by inhibiting the deSUMOylation of hnRNPK mediated by SUMO specific peptidase 2 and then regulating the sequence-specific DNA binding ability of the hnRNPK-p53 transcriptional complex.ConclusionsCirc-GALNT16 suppressed CRC progression via inhibiting Serpine1 expression through adjusting the sequence-specific DNA binding ability of the SENP2-mediated hnRNPK-p53 transcriptional complex and might work as a biomarker and therapeutic target for CRC.

Ubiquitin-conjugating enzyme E2 J1 (UBE2J1) has been proved to participate in the ubiquitination of multiple substrate proteins. However, the underlying mechanisms of UBE2J1 as a ubiquitin-conjugating enzyme participating in cancer development and progression remain largely unknown. Here, we identified that UBE2J1 was downregulated in colorectal cancer (CRC) tissues and cell lines which were mediated by DNA hypermethylation of its promoter, and decreased UBE2J1 was associated with poor prognosis. Functionally, UBE2J1 serving as a suppressor gene inhibited proliferation and metastasis of CRC cells. Mechanistically, UBE2J1-TRIM25, forming an E2-E3 complex, physically interacted and targeted RPS3 for ubiquitination and degradation at the K214 residue. The downregulated RPS3 caused by UBE2J1 overexpression restrained NF-κB translocation into the nucleus and therefore inactivates the NF-κB signaling pathway. Our study revealed a novel role of UBE2J1 mediated RPS3 poly-ubiquitination and degradation in disrupting the NF-κB signaling pathway, which may serve as a novel and promising biomarker and therapeutic target for CRC.

Background: N4-acetylcytidine (ac4C) as a significant RNA modification has been reported to maintain the stability of mRNA and to regulate the translation process. However, the roles of both ac4C and its ‘writer’ protein N-acetyltransferase 10 (NAT10) played in the disease especially colorectal cancer (CRC) are unclear. At this point, we discover the underlying mechanism of NAT10 modulating the progression of CRC via mRNA ac4C modification.Methods: The clinical significance of NAT10 was explored based on the TCGA and GEO data sets and the 80 CRC patients cohort of our hospital. qRT-PCR, dot blot, WB and IHC were performed to detect the level of NAT10 and ac4C modification in CRC tissues and matched adjacent tissues. CCK-8, colony formation, transwell assay, mouse xenograft and other in vivo and in vitro experiments were conducted to probe the biological functions of NAT10. The potential mechanisms of NAT10 in CRC were clarified by RNA-seq, RIP-seq, acRIP-seq, luciferase reporter assays, etc. Results: The levels of NAT10 and ac4C modification were significantly upregulated. Also, the high expression of NAT10 had important clinical values like poor prognosis, lymph node metastasis, distant metastasis, etc. Furthermore, the in vitro experiments showed that NAT10 could inhibit apoptosis and enhance the proliferation, migration and invasion of CRC cells and also arrest them in the G2/M phase. The in vivo experiments discovered that NAT10 could promote tumor growth and liver/lung metastasis. In terms of mechanism, NAT10 could mediate the stability of KIF23 mRNA by binding to its mRNA 3’UTR region and up-regulating its mRNA ac4c modification. And then the protein level of KIF23 was elevated to activate the Wnt/β-catenin pathway and more β-catenin was transported into the nucleus which led to the CRC progression. Besides, the inhibitor of NAT10, remodelin, was applied in vitro and vivo which showed an inhibitory effect on the CRC cells.Conclusions: NAT10 promotes the CRC progression through the NAT10/KIF23/GSK-3β/β-catenin axis and its expression is mediated by GSK-3β which forms a feedback loop. Our findings provide a potential prognosis or therapeutic target for CRC and remodelin deserves more attention.