Interplay between transcriptional and post-transcriptional regulation of Cyp2a5 expression

Biochem Pharmacol. 2003 May 15;65(10):1653-61. doi: 10.1016/s0006-2952(03)00118-7.


The cytochrome P450 (Cyp) 2a5 gene can be upregulated transcriptionally or by mRNA stabilization. The heterogeneous nuclear ribonucleoprotein (hnRNP) A1 interacting with the CYP2A5 mRNA has been shown to be a key post-transcriptional regulator of the Cyp2a5 gene. The aim of this study was to investigate if the transcriptional and post-transcriptional steps of Cyp2a5 expression are linked. This was done by modifying the transcription rate with transcriptional inducers (phenobarbital and cyclic AMP) and inhibitors (actinomycin D and 5,6-dichloro-1-beta-d-ribofuranosylbenzimidazole) and analyzing the effects upon post-transcriptional events. We found that inhibition of transcription led to relocalization of hnRNP A1 from the nucleus to the cytoplasm, to its strongly increased binding to the cytoplasmic CYP2A5 mRNA and to CYP2A5 mRNA stabilization. In contrast, stimulated transcription resulted in increased binding of nuclear hnRNP A1 to the Cyp2a5 promoter, and overexpression of hnRNP A1 led to stimulated transcription of a Cyp2a5 promoter-driven luciferase recombinant. This strongly suggests that the transcriptional and post-transcriptional stages of Cyp2a5 expression are interrelated and that the nucleocytoplasmic shuttling hnRNP A1 may coordinate these different steps.

MeSH terms

  • Animals
  • Aryl Hydrocarbon Hydroxylases / genetics*
  • Aryl Hydrocarbon Hydroxylases / metabolism
  • Base Sequence
  • Cytochrome P-450 CYP2A6
  • Cytochrome P450 Family 2
  • DNA / analysis
  • Gene Expression Regulation, Enzymologic*
  • Genes, Reporter
  • Heterogeneous-Nuclear Ribonucleoprotein Group A-B / metabolism*
  • Male
  • Mice
  • Mice, Inbred DBA
  • Mixed Function Oxygenases / genetics*
  • Mixed Function Oxygenases / metabolism
  • Molecular Sequence Data
  • Promoter Regions, Genetic / physiology*
  • RNA Stability
  • RNA, Messenger / metabolism
  • Transcription, Genetic*


  • Heterogeneous-Nuclear Ribonucleoprotein Group A-B
  • RNA, Messenger
  • DNA
  • Mixed Function Oxygenases
  • Aryl Hydrocarbon Hydroxylases
  • Cyp2a5 protein, mouse
  • Cytochrome P-450 CYP2A6
  • Cytochrome P450 Family 2