Characterization of c-myc 3' to 5' mRNA decay activities in an in vitro system.
The levels of mRNA and protein encoded by the c-myc protooncogene set the balance between proliferation and differentiation of mammalian cells. Thus, it is essential for the cell to tightly control c-myc expression. Indeed, cells utilize many mechanisms to control c-myc expression, including transcription, RNA processing, translation, and protein stability. We have focused on turnover of c-myc mRNA as a key modulator of the timing and level of c-myc expression. c-myc mRNA is labile in cells, and its half-life is controlled by multiple instability elements located within both the coding region and the 3'-untranslated region (3'-UTR). Much work has focused on the protein factors that bind the instability elements, yet little is known about the enzymatic activities that effect the degradation of c-myc mRNA. Here I have utilized a novel cell-free mRNA decay system to characterize the c-myc mRNA decay machinery. This machinery consists of 3' to 5' mRNA decay activities that are Mg2+-dependent, require neither exogenous ATP/GTP nor an ATP-regenerating system, and act independently of a 7mG(5')ppp(5')G cap structure to deadenylate an exogenous mRNA substrate in a c-myc 3'-UTR-dependent fashion. Following deadenylation, nucleolytic decay of the 3'-UTR occurs generating 3' decay intermediates via a ribonucleolytic activity that can assemble on the c-myc 3'-UTR in a poly(A)-independent manner.
Brewer
G
G
Department of Microbiology and Immunology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157-1064, USA. gbrewer@wfubmc.edu
D020413:3' Untranslated Regions; D002474:Cell-Free System; D015972:Gene Expression Regulation, Neoplastic; D005914:Globins / Q000096:biosynthesis / Q000235:genetics; D006207:Half-Life; D006801:Humans; D011132:Polyribosomes / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism*; D012334:RNA, Neoplasm / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics
D020413:3' Untranslated Regions; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D011993:Recombinant Fusion Proteins; D005914:Globins