Concerted action of poly(A) nucleases and decapping enzyme in mammalian mRNA turnover.
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.
Yamashita
Akio
A
Department of Biochemistry and Molecular Biology, The University of Texas Medical School, Houston, Texas 77030, USA.
Chang
Tsung-Cheng
TC
Yamashita
Yukiko
Y
Zhu
Wenmiao
W
Zhong
Zhenping
Z
Chen
Chyi-Ying A
CY
Shyu
Ann-Bin
AB
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*
D004722:Endoribonucleases; D005095:Exoribonucleases; D005914:Globins; D012333:RNA, Messenger; C030052:mRNA decapping enzymes