Microarray analysis reveals Tmub1 as a cell cycle-associated protein in rat hepatocytes.

Transmembrane and ubiquitin-like domain containing protein 1 (Tmub1), formerly known as hepatocyte odd protein shuttling (HOPS) has been recognized as a ubiquitously expressed shuttling protein that moves between the nucleus and cytoplasm in hepatocytes. Tmub1 is involved in liver regeneration and functions as a bridging protein in tumor cell proliferation. To investigate the transcriptional profile and potential biological processes affected by Tmub1 expression in normal rat hepatocytes, microarray and bioinformatics experiments were used to identify 127 mRNAs differentially expressed between Tmub1­overexpression, Tmub1­knockdown and normal BRL­3A cells (fold­change ≥2.5). The expression levels of 17 key node genes associated with the cell cycle were confirmed by reverse transcription-quantitative polymerase chain reaction analysis. Flow cytometry, 5­Ethynyl­20­deoxyuridine, Cell Counting Kit­8 and western blotting experiments revealed the effects on the cell cycle and the inhibition of proliferation in BRL­3A cells overexpressing Tmub1. Further co­immunoprecipitation assays demonstrated that Tmub1 interacts with cyclin A2 during the cell cycle and that the overexpression of Tmub1 may postpone cyclin A2 and cyclin B1 degradation in the M phase. The results of the present study indicated that Tmub1 functions as a cell proliferation inhibitor and cell cycle­associated protein.

A novel miR-219-SMC4-JAK2/Stat3 regulatory pathway in human hepatocellular carcinoma.

BACKGROUND: To understand the involvement of structural maintenance of chromosome 4 (SMC4) in the development and progression of hepatocellular carcinoma (HCC). METHODS: Real-time quantitative PCR and Western Blotting were applied to measure the expression of SMC4 in HCC samples and cell lines. The tumor-promoting effect of SMC4 was determined by WST-1, soft agar colony formation, cell motility and invasion assays. The SMC4 target signal pathway was identified by luciferase reporter and real-time quantitative PCR assays. RESULTS: The upregulation of SMC4 was frequently detected in HCC samples and cell lines. Functional assays demonstrated that SMC4 could effectively promote tumor cell growth rate, colony formation in soft agar, wound-healing and invasion. Further studies showed that increased miR-219 levels caused a significant decrease in the SMC4 expression, and SMC4 inhibitor downregulated JAK2/Stat3 expression at both the mRNA and protein levels. CONCLUSIONS: Our findings provide new insight into SMC4 function and the mechanisms of growth and invasion of HCC.