Roles Of β1Subunit In Tumorigenesis

The ubiquitin-proteasome system (UPS) is an important protein regulatory system in eukaryotes, which involves degradation of most proteins, so it plays a key role in cell biological process, β1is a subunit of20S catalytic complex, it has caspase-like activity, and cuts preferentially after acidic residues. Previous study has shown that β1is up-regulated in hepatocellular carcinoma tissues, but the function of β1in tumorigenesis remains unclear.In the present study, we also detect that β1is up-regulated in oesophageal cancer tissues and most ovarian cancer cell lines, but other subunits such as Rpt3has no changes. In order to explore the role of β1in cancer, cell proliferation assay and clone formation assay are used, we observe that overexpression of β1can promote cell proliferation. We next find β1can enhance cell migration in wound healing assay. Recent study has reported that β1can degrade p27kip1, however it is uncertain how β1influences the degradation. We test whether overexpression of exogenous β1and β1shRNA can influence the expression of p27kip1, the results show that β1can regulate p27kip1, and these two proteins present negative correlation. Next, both immunoprecipitation and GST-pull down assay indicate that β1and p27kip1have interaction directly. Interestingly, β1interacts with a7, and α7is down-regulated upon siβ1. In conclusion, our study first proposes that β1is a new onco-protein, and is likely to play a crucial role in tumorigenesis through p27kip1degradation.