title: Inhibition of Smurf2 translation by miR-322/503 modulates TGF-β/Smad2 signaling and intestinal epithelial homeostasis.
abstract: Smad ubiquitin regulatory factor 2 (Smurf2) is an E3 ubiquitin ligase that regulates transforming growth factor β (TGF-β)/Smad signaling and is implicated in a wide variety of cellular responses, but the exact mechanisms that control Smurf2 abundance are largely unknown. Here we identify microRNA-322 (miR-322) and miR-503 as novel factors that regulate Smurf2 expression posttranscriptionally. Both miR-322 and miR-503 interact with Smurf2 mRNA via its 3'-untranslated region (UTR) and repress Smurf2 translation but do not affect total Smurf2 mRNA levels. Studies using heterologous reporter constructs reveal a greater repressive effect of miR-322/503 through a single binding site in the Smurf2 3'-UTR, whereas point mutation of this site prevents miR-322/503-induced repression of Smurf2 translation. Increased levels of endogenous Smurf2 via antagonism of miR-322/503 inhibits TGF-β-induced Smad2 activation by increasing degradation of phosphorylated Smad2. Furthermore, the increase in Smurf2 in intestinal epithelial cells (IECs) expressing lower levels of miR-322/503 is associated with increased resistance to apoptosis, which is abolished by Smurf2 silencing. These findings indicate that miR-322/503 represses Smurf2 translation, in turn affecting intestinal epithelial homeostasis by altering TGF-β/Smad2 signaling and IEC apoptosis.
authors.affiliation: Cell Biology Group, Department of Surgery, University of Maryland School of Medicine, Baltimore, MD 21201 Department of Pathology, University of Maryland School of Medicine, Baltimore, MD 21201 Baltimore Veterans Affairs Medical Center, Baltimore, MD 21201 Laboratory of Genetics, National Institute on Aging-Intramural Research Program, National Institutes of Health, Baltimore, MD 21224.
authors.forename: Shan
authors.initials: S
authors.lastname: Cao
authors.forename: Lan
authors.initials: L
authors.lastname: Xiao
authors.forename: Jaladanki N
authors.initials: JN
authors.lastname: Rao
authors.forename: Tongtong
authors.initials: T
authors.lastname: Zou
authors.forename: Lan
authors.initials: L
authors.lastname: Liu
authors.forename: Dee
authors.initials: D
authors.lastname: Zhang
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Turner
authors.forename: Myriam
authors.initials: M
authors.lastname: Gorospe
authors.forename: Jian-Ying
authors.initials: JY
authors.lastname: Wang
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D000818:Animals; D017209:Apoptosis / Q000235:genetics; D002460:Cell Line; D003513:Cycloheximide / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000378:metabolism; D035683:MicroRNAs / Q000037:antagonists & inhibitors / Q000235:genetics*; D010766:Phosphorylation; D014176:Protein Biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D015398:Signal Transduction; D051899:Smad2 Protein / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000494:pharmacology; D044767:Ubiquitin-Protein Ligases / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D020413:3' Untranslated Regions; C585349:MIRN322 microRNA, rat; C571410:MIRN503 microRNA, rat; D035683:MicroRNAs; D012333:RNA, Messenger; D051899:Smad2 Protein; C497784:Smad2 protein, rat; D016212:Transforming Growth Factor beta; D003513:Cycloheximide; C526200:Smurf2 protein, rat; D044767:Ubiquitin-Protein Ligases