Research On Phosphorylation Of Nuclear Matrix-binding Protein SATB1 By Akt1 And Its Functions

Akt is a serine/thronine kinase. The protein kinase Akt acts as the major downstream target of P1-3K and regulates the biological function of cells. Those Akt substrates,such as GSK-3,Bad,caspase9,NF-κB and p27kip1, that are most likely to contribute to the diverse cellular roles of Akt, which include cell survival, growth and proliferation. Indeed, recent studies have revealed that Akt plays important role in tumorigenesis and metastasis. Frequent aberrant activation of Akt can promote tumorigenesis by blocking apoptosis. The important role of Akt in human physiology and disease has made it a researching target.SATB1 (special AT-rich sequences binding protein 1) is polymerized and forms a cage-like structure surrounding heterochromatin, whereby it tethers nuclear matrix and matrix attachment region through direct binding, dynamically orchestrating chromatin DNA loop formation. Signaling events trigger phosphorylation, acetylation, and sumoylation on SATB1, thereby either modulating its DNA binding ability or changing its intranuclear localization. SATB1 associates with a number of molecules, recruits chromatin remodeling complexes and histone modifying enzymes and regulates gene expression temporospatially. This review highlights the roles of SATB1 in cell differentiation, apoptosis, tumor growth, metastasis, and X chromosome inactivation. SATB1 holds promise in clinical therapeutics, particularly cancer metastasis treatment.Previous studies have confirmed that SATB1 can be phosphorylatied by PKC which is related to SATB1 transcription ability. We speculate that the human and mouse SATB1 can be phosphorylated by Akt1 based on existing research and data of Scansite. As the data shown, SATB1 contains three candidate phosphorylation sites, namely S47 (RGRLGST) and S557 (IRRFLSL). Our research aims at exploring the relationship between Akt1 and SATB1. First, the cDNA encoding human SATB1 was sub-cloned into expression vector pcDNA4 We explored the relationship between Aktl and SATB1 using immunoprecipitation and western blot. Then the S47 of SATB1 was mutated to S47A and S47D. Study whether Aktl phosphorylates SATB1 at serine 47 sites by in-vitro kinase assay. At the same time, we identified whether Akt1 interacts with SATB1 using co-immunoprocipition and GST-pull down assay. Finally, we constructed pGFP-N2/SATB1 and studied the effects of phosphorylation of SATB1 by Aktl on its intracellular distribution and stability.We had the conclution from the study. First, Aktl phosphorylates SATB1 at serine 47 site specifically.Second, there is no interaction between Aktl and SATB1.Finally, phosphorylation of SATB1 by Akt1 impacts its own stability. Study of the molecular mechanisms of Aktl involved in regulating the normal physiological state and disease has important physiological and pathological significance.