title: Post-transcriptional regulation of hepatic NADPH-cytochrome P450 reductase by thyroid hormone: independent effects on poly(A) tail length and mRNA stability.
abstract: Thyroid hormone [triiodothyronine (T3)] positively regulates NADPH cytochrome P450 reductase (P450R) mRNA expression in rat liver, with P450R transcription initiation being a key regulated step. T3 is presently shown to have significant post-transcriptional effects on P450R expression. T3 increased the size of cytoplasmic P450R mRNA by approximately 105 nucleotides 12 h after T3 treatment, followed by a return to basal levels at 24 h. Primer extension analysis and Northern hybridization with 5'-untranslated region probes revealed no change in P450R mRNA 5' structure with T3 treatment. By contrast, RNase H analysis revealed a transient, T3-induced increase in P450R mRNA poly(A) tail, from approximately 100 to approximately 205 A. This increase in P450R polyadenylation, detectable in the nucleus 8 h after T3 treatment and in the cytoplasm at 12 h, was transient and was reversed by 16 h, when the T3-induced accumulation of cytoplasmic P450R mRNA was near maximal. Actinomycin D blocked the increase in P450R poly(A) tail and the induction of P450R mRNA, indicating a requirement for ongoing gene transcription for both T3 responses. T3 treatment destabilized P450R mRNA in rat liver in vivo, as shown by the T3-dependent 6-fold decrease in cytoplasmic P450R mRNA half-life, from a basal value of >or=16 h in uninduced liver to approximately 2.5 h, measured 24 h after T3 administration. These findings demonstrate that T3 increases nuclear polyadenylation of P450R RNA as a transient, early regulatory response and that this response is temporally dissociated from the subsequent decrease in cytoplasmic P450R mRNA stability.
authors.affiliation: Division of Cell and Molecular Biology, Department of Biology, Boston University, Boston, Massachusetts, USA.
authors.forename: Dongxu
authors.initials: D
authors.lastname: Liu
authors.forename: David J
authors.initials: DJ
authors.lastname: Waxman
mesh_terms: D020413:3' Untranslated Regions / Q000378:metabolism; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D006207:Half-Life; D008297:Male; D009251:NADPH-Ferrihemoprotein Reductase / Q000235:genetics* / Q000378:metabolism; D011061:Poly A / Q000235:genetics*; D026723:Polyadenylation / Q000187:drug effects; D020871:RNA Stability / Q000187:drug effects; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D016914:Ribonuclease H / Q000378:metabolism; D013963:Thyroid Hormones / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects; D014284:Triiodothyronine / Q000494:pharmacology*
chemical_list: D020413:3' Untranslated Regions; D012333:RNA, Messenger; D013963:Thyroid Hormones; D014284:Triiodothyronine; D011061:Poly A; D009251:NADPH-Ferrihemoprotein Reductase; D016914:Ribonuclease H