CTG triplet repeats from the myotonic dystrophy gene are expanded in escherichia coli distal to the replication origin as a single large event

Seong Man Kang, Keiichi Ohshima, Adam Jaworski, Robert D. Wells

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The expansion and contraction of CTG and CGG trinucleotide repeat sequences have been associated with several heritable genetic diseases. We developed a system for investigating the expansion of triplet repeat sequences in Escherichia coli in order to elucidate molecular mechanisms. Analysis of expanded regions using the interrupting CTA triplet sequence as a location marker within the CTG tract revealed that the expansion of large CTG repeats is one event rather than an accumulation of multiple small expansions and that the expansions occur more frequently in the region distal from the replication origin. Also, we showed that a loss of interruptions increases the expansion frequency. Thus, the instability of large triplet repeats in hereditary diseases occurs by a mechanism different from the instability in microsatellite sequences caused by defects in mismatch repair systems for certain sporadic cancers and hereditary non-polyposis colorectal cancers.

Original languageEnglish
Pages (from-to)543-547
Number of pages5
JournalJournal of Molecular Biology
Issue number4
Publication statusPublished - 1996 May 17
Externally publishedYes



  • Expansions
  • Interruption sequences
  • Mechanism
  • Slippage
  • Triplet repeats

ASJC Scopus subject areas

  • Virology

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