Mechanism Research Of Regulating Gene Expression Via E2Ubiquitin Conjugating Enzyme RAD6during Cell Cycle

Cell cycle is a continuous process from one end of mitosis to the next end, in which one cell divides into two identical daughter cells. To ensure the accuracy of the entire process, gene expression relating cell cycle must be in the precise control so as to ensure the orderly operation of the various events during cell cycle progress.Protein ubiquitination plays crucial roles in protein degradation and protein functional regulation. It usually needs three kinds of enzymes to participate in the modification process:El ubiquitin activating enzyme, E2ubiquitin conjugating enzyme and E3ubiquitin-protein ligase. These three enzymes can synergistically modify protein through different forms of ubiquitination (monoubiquitination or polyubiquitination). Now, more and more studies have intimate knowledge of protein ubiquitination. Generally believing is that protein ubiquitination will lead to the degradation of the protein. In vivo, protein with polyubiquitination tag will be broken down through the ubiquitin-proteasome pathway. Monoubiquitination has more complicated effect on the protein. It does not generally lead to the degradation of protein substrates, but can regulate their biological functions. RAD6is an important E2ubiquitin conjugating enzyme, which widely participates in various biological processes, such as DNA damage repair, histone modification and gene expression.In human liver cells HL-7702, our research reports that the overexpression of RAD6can promotes G1-S transition and cell proliferation. Because many articles have reported that the cell cycle protein D1(CCND1) is the key factor to determine a critical factor in G1-S transition and cell proliferation. We guess that RAD6can regulate the expression of CCND1. Then this hypothesis can be proved to be right via our experiments. Meanwhile, we further demonstrate that RAD6regulates the transcription of CCND1probably through affecting H2B monoubiquitination and H3K4me3levels at CCND1promoter region. Moreover, Kaplan-Meier plotter survival rate assay and expressional level assay suggested that RAD6and CCND1are positively correlated with each other in clinical samples of breast cancer patients.In conclusion, our research has provided evidence that RAD6can regulate cell cycle progression and cell proliferation through regulating CCND1expression in human cells. This molecular mechanism will replenish the blank of the basic theory. Meanwhile, RAD6and CCND1would also be new molecular markers for breast cancer molecular diagnosis and prognosis. It also has important application value for clinical medicine.