title: Concerted action of poly(A) nucleases and decapping enzyme in mammalian mRNA turnover.
abstract: In mammalian cells, the enzymatic pathways involved in cytoplasmic mRNA decay are incompletely defined. In this study, we have used two approaches to disrupt activities of deadenylating and/or decapping enzymes to monitor effects on mRNA decay kinetics and trap decay intermediates. Our results show that deadenylation is the key first step that triggers decay of both wild-type stable and nonsense codon-containing unstable beta-globin mRNAs in mouse NIH3T3 fibroblasts. PAN2 and CCR4 are the major poly(A) nucleases active in cytoplasmic deadenylation that have biphasic kinetics, with PAN2 initiating deadenylation followed by CCR4-mediated poly(A) shortening. DCP2-mediated decapping takes place after deadenylation and may serve as a backup mechanism for triggering mRNA decay when initial deadenylation by PAN2 is compromised. Our findings reveal a functional link between deadenylation and decapping and help to define in vivo pathways for mammalian cytoplasmic mRNA decay.
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Texas Medical School, Houston, Texas 77030, USA.
authors.forename: Akio
authors.initials: A
authors.lastname: Yamashita
authors.forename: Tsung-Cheng
authors.initials: TC
authors.lastname: Chang
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Yamashita
authors.forename: Wenmiao
authors.initials: W
authors.lastname: Zhu
authors.forename: Zhenping
authors.initials: Z
authors.lastname: Zhong
authors.forename: Chyi-Ying A
authors.initials: CY
authors.lastname: Chen
authors.forename: Ann-Bin
authors.initials: AB
authors.lastname: Shyu
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology; D003593:Cytoplasm / Q000378:metabolism; D004722:Endoribonucleases / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D005095:Exoribonucleases / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D005347:Fibroblasts / Q000201:enzymology; D005914:Globins / Q000235:genetics; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D034622:RNA Interference; D020871:RNA Stability / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism*
chemical_list: D004722:Endoribonucleases; D005095:Exoribonucleases; D005914:Globins; D012333:RNA, Messenger; C030052:mRNA decapping enzymes