Skp2 Promotes APL Progression Through Stabilizing PML-RARα Protein To Suppress JunB

Objectives:To investigate the correlation between the expression of Skp2 and Jun B and its regulatory mechanism in APL process.Methods:Upon targeting Skp2 knockdown in NB4 cells,the expression of Jun B regulated by Skp2 was determined by western blot,real-time fluorescence quantitative polymerase chain reaction assay,and the effects of Skp2 expression changes on APL cell proliferation and differentiation were analyzed by CCK-8 assay and flow cytometry.According to the results of dual luciferase and chromatin immunoprecipitation analysis confirmed that PML-RARαinhibits the transcriptional activation function of PU.1 by forming a complex with it,which blocked the Jun B promoter activated by PU.1.Skp2 regulates the stabilization of PML-RARαprotein through autophagy was verified by protein immunoprecipitation and related experiments.In vitro and in vivo experiments showed that the small molecule inhibitors targeting Skp2 can enhance the ability of apoptosis and differentiation induced by ATRA in NB₄cells.Results:After Skp2 knockdown in NB₄ cells with specific small interfering RNA and lentivirus,cell proliferation was reduced,autophagy flux was upregulated,and ATRA induced differentiation was enhanced.Reduced the expression of Skp2 and upregulated the expression of PU.1 have similar abilities to regulate certain proteins related to cell proliferation and apoptosis.Jun B is one of the targets gene of PU.1 and the expression is negatively correlated with Skp2 was demonstrated in vivo.Overexpression of Jun B inhibited proliferation and enhanced ATRA induced differentiation of NB₄ cells,while knockdown of Jun B showed the opposite phenotype.Further investigation into the molecular mechanism of Jun B regulated by Skp2 revealed that PML-RARαcould exert its transcriptional suppression function to inhibit the transactivation of Jun B,and Skp2 could regulate the stability of PML-RARαprotein through autophagy.The regulation of autophagy may be realized through the lnc RNA HOTAIRM1 and AKT/GSK3βsignaling pathways.Small molecule inhibitors targeting Skp2 have been shown to inhibit cell growth in vivo and in vitro.Conclusion:High expression of Skp2 inhibiting the expression level of Jun B by maintaining PML-RARαprotein stability in NB₄ cells.The stability of PML-RARαprotein is regulated by autophagy-associated selective ubiquitination and inhibition of GSK 3βkinase activity.Therefore,we speculated that Skp2 can regulate the expression of PML-RARαthrough multiple pathways and affect the level of Jun B.The therapy of targeting Skp2enhanced the sensitivity of ATRA,and Skp2 is expected to become a new therapeutic target for APL.