Evidence for a 3'-5' decay pathway for c-myc mRNA in mammalian cells.
Many mRNAs in mammalian cells decay via a sequential pathway involving rapid conversion of polyadenylated molecules to a poly(A)-deficient state followed by rapid degradation of the poly(A)-deficient molecules. However, the rapidity of this latter step(s) has precluded further analyses of the decay pathways involved. Decay intermediates derived from degradation of poly(A)-deficient molecules could offer clues regarding decay pathways, but these intermediates have not been readily detected. Cell-free mRNA decay systems have proven useful in analyses of decay pathways because decay intermediates are rather stable in vitro. Cell-free systems indicate that many mRNAs decay by a sequential 3'-5' pathway because 3'-terminal decay intermediates form following deadenylation. However, if 3'-terminal, in vitro decay intermediates reflect a biologically significant aspect of mRNA turnover, then similar intermediates should be present in cells. Here, I have compared the in vivo and in vitro decay of mRNA encoded by the c-myc proto-oncogene. Its decay both in vivo and in vitro occurs by rapid removal of the poly(A) tract and generation of a 3'-terminal decay intermediate. These data strongly suggest that a 3'-5' pathway contributes to turnover of c-myc mRNA in cells. It is likely that 3'-5' decay represents a major turnover pathway in mammalian cells.
Brewer
G
G
Department of Microbiology and Immunology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157-1064, USA. gbrewer@wfubmc.edu
D001483:Base Sequence; D004591:Electrophoresis, Polyacrylamide Gel; D016259:Genes, myc / Q000235:genetics*; D006801:Humans; D008957:Models, Genetic; D008969:Molecular Sequence Data; D000090063:Proto-Oncogene Mas; D012333:RNA, Messenger / Q000378:metabolism*; D016914:Ribonuclease H / Q000378:metabolism; D014407:Tumor Cells, Cultured
C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D012333:RNA, Messenger; D016914:Ribonuclease H