In vivo generation of 3' and 5' truncated species in the process of c-myc mRNA decay.
It has been demonstrated that the half-life of c-myc mRNA is modulated in response to physiological agents. The elucidation of the decay process and the identification of the critical steps in the in vivo c-myc mRNA degradation pathway can be approached by following the fate of c-myc mRNA under the influence of such factors. IFN-alpha was the factor used to modulate c-myc mRNA half-life in HeLa 1C5 cells, a stable clone derived from HeLa cells. This cell line carries multiple copies of the c-myc gene, under the control of the dexamethasone inducible mouse mammary tumor virus-long terminal repeat (MMTV-LTR). Exposure of HeLa 1C5 cells to IFN-alpha resulted in a further 2-fold increase over the dexamethasone-induced c-myc mRNA. However, the c-myc mRNA in IFN-alpha treated cells was less stable than that in the control cells. RNase H mapping of the 3' untranslated region of c-myc mRNA revealed, in addition to the full length mRNA, three smaller fragments. These fragments were proven to be truncated, non-adenylated c-myc mRNA species generated in vivo. Exposure of HeLa 1C5 cells to Interferon-alpha before induction with dexamethasone resulted in the enhanced presence of these intermediates. RNase H analysis of c-myc mRNA after actinomycin D chase revealed that deadenylation led to the formation of a relatively more stable oligoadenylated c-myc mRNA population which did not appear to be precursor to the truncated intermediates. The detection of truncated 3' end c-myc mRNA adenylated fragments as well, implies that the c-myc mRNA degradation process may follow an alternative pathway possibly involving endonucleolytic cleavage.
Ioannidis
P
P
Institute of Biology, NCSR-Demokritos, Athens, Greece.
Havredaki
M
M
Courtis
N
N
Trangas
T
T
D000818:Animals; D005786:Gene Expression Regulation / Q000187:drug effects*; D016259:Genes, myc; D006367:HeLa Cells; D006801:Humans; D006868:Hydrolysis; D016898:Interferon-alpha / Q000494:pharmacology*; D051379:Mice; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*
D016898:Interferon-alpha; D012333:RNA, Messenger