Induction of cell proliferation, clonogenicity and cell accumulation in S phase as a consequence of human UBE2Q1 overexpression

Abstract

Ubiquitination is an important cellular mechanism with a pivotal role in the degradation of abnormal or short-lived proteins and the regulation of cell cycle and cell growth. The ubiquitin-proteasome pathway is altered in multiple types of human malignancies, including colorectal cancer (CRC). The alteration in the expression of the novel human gene ubiquitin-conjugating enzyme E2 Q1 (UBE2Q1), as a putative member of the E2 ubiquitin-conjugating enzyme family, has been reported in several malignancies, including carcinoma of the breast, hepatocellular and colorectal cancer, and pediatric acute lymphoblastic leukemia. In the present study, the effect of UBE2Q1 overexpression on cell growth, clonogenicity, motility and cell cycle was investigated in a CRC cell line. The UBE2Q1 gene was cloned in the pCMV6-AN-GFP expression vector. A series of stable transfectants of SW1116 cells overexpressing UBE2Q1 protein were established and confirmed by fluorescence microscopy and western blotting. Using these cells, MTT assay was performed to evaluate cell growth and proliferation, while crystal violet staining was used for clonogenicity assay. Cell cycle analysis was also performed to survey the ratio of cells accumulated in different phases of the cell cycle upon transfection. The motility of these cells was also studied using wound healing assay. UBE2Q1 transfectants exhibited a faster growth in cell culture, increased colony formation capacity and enhanced motility compared with control non-transfected cells and cells transfected with empty vector (mock-transfected cells). UBE2Q1 overexpression also resulted in a significant decrease in the number of cells accumulated in the G0/G1 phase of the cell cycle. The present findings suggest that UBE2Q1 may function as an oncogene that induces proliferation of cancer cells, and could be a novel diagnostic tool and a potential therapeutic target for CRC.