title: A 6 bp polymorphism in the thymidylate synthase gene causes message instability and is associated with decreased intratumoral TS mRNA levels.
abstract: OBJECTIVE
  A 6 bp deletion polymorphism in the thymidylate synthase (TS) gene was investigated in order to determine its function.
  
  
  METHODS
  A luciferase system was used to investigate the function of the 6 bp/1494 polymorphism in vitro. A group of 43 patients with colorectal carcinoma were evaluated for the 6 bp/1494 polymorphism and for intratumoral TS mRNA levels in vivo.
  
  
  RESULTS
  The 3'UTR of TS containing the +6 bp polymorphism resulted in an approximate 35% decrease in luciferase activity and mRNA levels, while the TS-3'UTR bearing the -6 bp deletion resulted in an approximate 70% decrease in luciferase activity and mRNA levels. The TS-3'UTR construct containing the -6 bp/1494 deletion also had a higher rate of message degradation compared to the +6 bp/1494 construct. Individuals homozygous for the insertion (+6 bp/+6 bp) had significantly higher TS mRNA levels compared to individuals that were homozygous for the deletion (-6 bp/-6 bp) (P < 0.007). We determined the frequency of the -6 bp/1494 deletion polymorphism to be 41% in non-Hispanic whites, 26% in Hispanic whites, 52% in African-Americans and 76% in Singapore Chinese.
  
  
  CONCLUSIONS
  These results suggest that the -6 bp/1494 deletion polymorphism in the 3'UTR of TS is associated with decreased mRNA stability in vitro and lower intratumoral TS expression in vivo. Further, the 6 bp/1494 polymorphism varies greatly within different ethnic populations and is in linkage disequilibrium with the TS 5' tandem repeat enhancer polymorphism. Taken together, these data suggest that the 6 bp/1494 polymorphism may be a useful screening tool in predicting TS mRNA expression.
authors.affiliation: Department of Molecular Biology, The University of Medicine and Dentistry of New Jersey, School of Osteopathic Medicine, Stratford, New Jersey 08084, USA.
authors.forename: Michael V
authors.initials: MV
authors.lastname: Mandola
authors.forename: Jan
authors.initials: J
authors.lastname: Stoehlmacher
authors.forename: Wu
authors.initials: W
authors.lastname: Zhang
authors.forename: Susan
authors.initials: S
authors.lastname: Groshen
authors.forename: Mimi C
authors.initials: MC
authors.lastname: Yu
authors.forename: Syma
authors.initials: S
authors.lastname: Iqbal
authors.forename: Heinz-Josef
authors.initials: HJ
authors.lastname: Lenz
authors.forename: Robert D
authors.initials: RD
authors.lastname: Ladner
mesh_terms: D020413:3' Untranslated Regions; D001483:Base Sequence; D002460:Cell Line; D015179:Colorectal Neoplasms / Q000201:enzymology*; D017931:DNA Primers; D004742:Enhancer Elements, Genetic; D005006:Ethnicity / Q000235:genetics; D006801:Humans; D011110:Polymorphism, Genetic; D012333:RNA, Messenger / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017384:Sequence Deletion; D020080:Tandem Repeat Sequences; D013940:Thymidylate Synthase / Q000235:genetics*
chemical_list: D020413:3' Untranslated Regions; D017931:DNA Primers; D012333:RNA, Messenger; D013940:Thymidylate Synthase