Regulation of heme oxygenase-1 mRNA deadenylation and turnover in NIH3T3 cells by nitrosative or alkylation stress.
BACKGROUND
Heme oxygenase-1 (HO-1) catalizes heme degradation, and is considered one of the most sensitive indicators of cellular stress. Previous work in human fibroblasts has shown that HO-1 expression is induced by NO, and that transcriptional induction is only partially responsible; instead, the HO-1 mRNA half-life is substantially increased in response to NO. The mechanism of this stabilization remains unknown.


RESULTS
In NIH3T3 murine fibroblasts, NO exposure increased the half-life of the HO-1 transcript from ~1.6 h to 11 h, while treatments with CdCl2, NaAsO2 or H2O2 increased the half-life only up to 5 h. Although poly(A) tail shortening can be rate-limiting in mRNA degradation, the HO-1 mRNA deadenylation rate in NO-treated cells was ~65% of that in untreated controls. In untreated cells, HO-1 poly(A) removal proceeded until 30-50 nt remained, followed by rapid mRNA decay. In NO-treated cells, HO-1 deadenylation stopped with the mRNA retaining poly(A) tails 30-50 nt long. We hypothesize that NO treatment stops poly(A) tail shortening at the critical 30- to 50-nt length. This is not a general mechanism for the post-transcriptional regulation of HO-1 mRNA. Methyl methane sulfonate also stabilized HO-1 mRNA, but that was associated with an 8-fold decrease in the deadenylation rate compared to that of untreated cells. Another HO-1 inducer, CdCl2, caused a strong increase in the mRNA level without affecting the HO-1 mRNA half-life.


CONCLUSIONS
The regulation of HO-1 mRNA levels in response to cellular stress can be induced by transcriptional and different post-transcriptional events that act independently, and vary depending on the stress inducer. While NO appears to stabilize HO-1 mRNA by preventing the final steps of deadenylation, methyl methane sulfonate achieves stabilization through the regulation of earlier stages of deadenylation.
Leautaud
Veronica
V
Department of Genetics and Complex Diseases, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA. veronica.leautaud.suderland@rice.edu
Demple
Bruce
B
D000227:Adenine Nucleotides / Q000378:metabolism*; D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D005786:Gene Expression Regulation / Q000235:genetics*; D006207:Half-Life; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism*; D008741:Methyl Methanesulfonate / Q000494:pharmacology; D051379:Mice; D041681:NIH 3T3 Cells; D009569:Nitric Oxide / Q000378:metabolism*; D020871:RNA Stability / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism*
D000227:Adenine Nucleotides; D012333:RNA, Messenger; D009569:Nitric Oxide; D008741:Methyl Methanesulfonate; D051547:Heme Oxygenase-1