title: Global analysis of posttranscriptional gene expression in response to sodium arsenite.
abstract: BACKGROUND
  Inorganic arsenic species are potent environmental toxins and causes of numerous health problems. Most studies have assumed that arsenic-induced changes in mRNA levels result from effects on gene transcription.
  
  
  OBJECTIVE
  We evaluated the prevalence of changes in mRNA stability in response to sodium arsenite in human fibroblasts.
  
  
  METHODS
  We used microarray analyses to determine changes in steady-state mRNA levels and mRNA decay rates following 24-hr exposure to noncytotoxic concentrations of sodium arsenite, and we confirmed some of these changes using real-time reverse-transcription polymerase chain reaction (RT-PCR).
  
  
  RESULTS
  In arsenite-exposed cells, 186 probe set-identified transcripts were significantly increased and 167 were significantly decreased. When decay rates were analyzed after actinomycin D treatment, only 4,992 (9.1%) of probe set-identified transcripts decayed by > 25% after 4 hr. Of these, 70 were among the 353 whose steady-state levels were altered by arsenite, and of these, only 4 exhibited significantly different decay rates between arsenite and control treatment. Real-time RT-PCR confirmed a major, significant arsenite-induced stabilization of the mRNA encoding δ aminolevulinate synthase 1 (ALAS1), the rate-limiting enzyme in heme biosynthesis. This change presumably accounted for at least part of the 2.7-fold increase in steady-state ALAS1 mRNA levels seen after arsenite treatment. This could reflect decreases in cellular heme caused by the massive induction by arsenite of heme oxygenase mRNA (HMOX1; 68-fold increase), the rate-limiting enzyme in heme catabolism.
  
  
  CONCLUSIONS
  We conclude that arsenite modification of mRNA stability is relatively uncommon, but in some instances can result in significant changes in gene expression.
authors.affiliation: Laboratory of Signal Transduction, National Institute of Environmental Health Sciences (NIEHS), National Institutes of Health (NIH), Department of Health and Human Services (DHHS), Research Triangle Park, North Carolina, USA.
authors.forename: Lian-Qun
authors.initials: LQ
authors.lastname: Qiu
authors.forename: Sarah
authors.initials: S
authors.lastname: Abey
authors.forename: Shawn
authors.initials: S
authors.lastname: Harris
authors.forename: Ruchir
authors.initials: R
authors.lastname: Shah
authors.forename: Kevin E
authors.initials: KE
authors.lastname: Gerrish
authors.forename: Perry J
authors.initials: PJ
authors.lastname: Blackshear
mesh_terms: D000624:5-Aminolevulinate Synthetase / Q000235:genetics / Q000378:metabolism*; D018053:Arsenites / Q000633:toxicity*; D002478:Cells, Cultured; D003609:Dactinomycin / Q000494:pharmacology; D004785:Environmental Pollutants / Q000633:toxicity*; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008297:Male; D012333:RNA, Messenger; D017670:Sodium Compounds / Q000633:toxicity*
chemical_list: D018053:Arsenites; D004785:Environmental Pollutants; D012333:RNA, Messenger; D017670:Sodium Compounds; D003609:Dactinomycin; C017947:sodium arsenite; D051547:Heme Oxygenase-1; D000624:5-Aminolevulinate Synthetase