Expression Regulation Of Tudor-SN Protein And Mechanism Of Participation In Protein Translation Regulation

Objectives: The expression regulation of eukaryotic gene which is a very complex process,occurs in DNA level,transcription level,protein translation level and other different levels.The expression regulation of genes in different levels,which may have different effects on the body biological functions.The preliminary study of our research group found that the expression of Tudor-SN protein in myocardium of adult mice was much lower than that in myocardium of one-day mice,but the expression of Tudor-SN m RNA was not significantly changed,that means,the expression of Tudor-SN protein in the process of myocardial maturation is regulated at the post-transcriptional level,but the specific mechanisms is still unclear.Here,we aimed at studying the expression mechanism of Tudor-SN protein in cardiomyocytes.In addition,we found that Tudor-SN is a new TOP gene which may be involved in the regulation of protein translation,so we intended to discuss the mechanism of Tudor-SN participating in protein translation.Methods: This project was divided into three parts: Part1,Construction of Tudor-SN UTR luciferase plasmids by gene recombination technique.The lipofectamine transfection and double luciferase assay were performed to detect the activity of luciferase in the Tudor-SN UTR luciferase recombinant plasmids.Part2,The DBTSS database was performed to analyze the transcription start site of Tudor-SN,and then we analyzed whether the 5'UTR region contained the 5'TOP sequences.The signal pathway inhibitor,Western Bloting,Real-Time PCR,density gradient centrifugation and polyribosomal curve analysis were performed to study the expression regulation mechanism of Tudor-SN.Part3,We analyzed the previous pull-down m RNA data of Tudor-SN protein,and the 5'UTR sequence of translation-related m RNAs which were bound to Tudor-SN protein.The lipofectamine transfection,Western Blotting and Real-Time PCR were used to detect the expression of related proteins after over-expression Tudor-SN.The mass spectrometry,Co IP and GST pull-down were performed to detect the translation initiation complex-related proteins that could bind to Tudor-SN protein.Results: Part1,(1)We successfully construct the luciferase plasmids of the Tudor-SN UTR.(2)The result from Double-luciferase assay confirme that the 5'UTR region of Tudor-SN has the highest activity to promote the expression of luciferase.Part2,(1)The 5'UTR region of Tudor-SN contains the 5'TOP sequences,moreover,the expression at translation level of Tudor-SN protein is mainly regulated by the PI3 K / AKT / m TOR signaling pathway in cardiomyocytes,so Tudor-SN is a TOP gene.(2)When PI3 K / AKT / m TOR signaling pathway is inhibited,the polyribosome of the experimental group is depolymerized compare with the control group,this means the translational efficiency of Tudor-SN is reduced.Part3,(1)The 5'UTR regions of many translation-related m RNAs which are combined with Tudor-SN protein contain the 5'TOP sequence.(2)Over-expression Tudor-SN promotes the expression of some translation-related proteins that bind to Tudor-SN protein.(3)The result from Mass spectrometry and Co IP experiments demonstrate that Tudor-SN protein can bind to translation-related proteins,GST pull-down experiments also show that Tudor-SN protein binds to these translation-related proteins through its SN domain.Conclusions: 1)The 5'UTR region of Tudor-SN can enhance the expression activity of many genes,contains the 5'TOP sequence.Moreover,the expression at translation level of Tudor-SN is regulated by the PI3 K / AKT / m TOR signaling pathway,so Tudor-SN is a TOP gene.2)Tudor-SN protein can bind to 5'TOP m RNA of many translation-related proteins,and over-expression Tudor-SN can promote the expression of translation these translation-related proteins.3)Tudor-SN protein is involved in the formation of e IF4 F translation initiation complex,in which the SN domain of Tudor-SN protein is the main functional fragment that mediates its formation.