哺乳动物TRIM71蛋白RNA结合特性的分子机制研究

Molecular mechanism governing RNA-binding property of mammalian TRIM71 protein

TRIM71 is an RNA-binding protein with ubiquitin ligase activity.Numerous functions of mammalian TRIM71,including cell cycle regulation,embryonic stem cell(ESC)self-renewal,and reprogramming of pluripotent stem cells,are related to its RNA-binding property.We previously reported that a long noncoding RNA(lnc RNA)Trincr1 interacts with mouse TRIM71(m TRIM71)to repress FGF/ERK pathway in mouse ESCs(m ESCs).Herein,we identify an RNA motif specifically recognized by m TRIM71 from Trincr1 RNA,and solve the crystal structure of the NHL domain of m TRIM71 complexed with the RNA motif.Similar to the zebrafish TRIM71,m TRIM71 binds to a stem-loop structured RNA fragment of Trincr1,and an adenosine base at the loop region is crucial for the m TRIM71 interaction.We map similar hairpin RNAs preferably bound by TRIM71 in the m RNA UTRs of the cell-cycle related genes regulated by TRIM71.Furthermore,we identify key residues of m TRIM71,conserved among mammalian TRIM71 proteins,required for the RNA-binding property.Single-site mutations of these residues significantly impair the binding of TRIM71 to hairpin RNAs in vitro and to m RNAs of Cdkn1a/p21 and Rbl2/p130 in m ESCs.Furthermore,congenital hydrocephalus(CH)specific mutation of m TRIM71 impair its binding to the RNA targets as well.These results reveal molecular mechanism behind the recognition of RNA by mammalian TRIM71 and provide insights into TRIM71 related diseases.