title: Dextran sodium sulfate inhibits the activities of both polymerase and reverse transcriptase: lithium chloride purification, a rapid and efficient technique to purify RNA.
abstract: BACKGROUND
  Dextran sodium sulfate (DSS) is commonly used in mouse studies to induce a very reproducible colitis that effectively mimics the clinical and histological features of human inflammatory bowel disease (IBD) patients, especially ulcerative colitis. However, the mechanisms of action of DSS remain poorly understood, and observations by our laboratory and other groups indicate that DSS contamination of colonic tissues from DSS-treated mice potently inhibits the quantitative reverse-transcription polymerase chain reaction (qRT-PCR) amplification of mRNA.
  
  
  RESULTS
  A prior study used poly-A-mediated mRNA purification to remove DSS from RNA extracts, but we herein report a second efficient and cost-effective approach to counteract this inhibition, using lithium chloride precipitation to entirely remove DSS from RNAs. We also explored how DSS interferes with qRT-PCR process, and we report for the first time that DSS can alter the binding of reverse transcriptase to previously primed RNA and specifically inhibits the enzymatic activities of reverse transcriptase and Taq polymerase in vitro. This likely explains why DSS-treated colonic RNA is not suitable to qRT-PCR amplification without a previous purification step.
  
  
  CONCLUSIONS
  In summary, we provide a simple method to remove DSS from colonic RNAs, and we demonstrate for the first time that DSS can inhibit the activities of both polymerase and reverse transcriptase. In order to reliably analyze gene expression in the colonic mucosa of DSS-treated mice, the efficiency rate of qRT-PCR must be the same between all the different experimental groups, including the water-treated control group, suggesting that whatever the duration and the percentage of the DSS treatment, RNAs must be purified.
authors.affiliation: Department of Biology, Center for Diagnostics and Therapeutics, Georgia State University, Atlanta GA 30303, USA. eviennois@gsu.edu.
authors.forename: Emilie
authors.initials: E
authors.lastname: Viennois
authors.forename: Fengyuan
authors.initials: F
authors.lastname: Chen
authors.forename: Hamed
authors.initials: H
authors.lastname: Laroui
authors.forename: Mark T
authors.initials: MT
authors.lastname: Baker
authors.forename: Didier
authors.initials: D
authors.lastname: Merlin
mesh_terms: D000818:Animals; D005591:Chemical Fractionation / Q000379:methods; D003092:Colitis / Q000139:chemically induced / Q000235:genetics / Q000473:pathology; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry*; D016264:Dextran Sulfate / Q000737:chemistry* / Q000494:pharmacology; D004195:Disease Models, Animal; D006801:Humans; D018021:Lithium Chloride / Q000737:chemistry*; D051379:Mice; D012333:RNA, Messenger / Q000235:genetics / Q000302:isolation & purification*; D012194:RNA-Directed DNA Polymerase / Q000737:chemistry*; D018894:Reverse Transcriptase Inhibitors / Q000737:chemistry*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000592:standards
chemical_list: D012333:RNA, Messenger; D018894:Reverse Transcriptase Inhibitors; D016264:Dextran Sulfate; D012194:RNA-Directed DNA Polymerase; D004259:DNA-Directed DNA Polymerase; D018021:Lithium Chloride