Current Microbiology

, Volume 20, Issue 2, pp 133–136 | Cite as

Expression of a DNA methylation (dam) gene inEscherichia coli K-12

  • Judy A. Arraj
  • Te-Hui Wu
  • M. G. Marinus
Article

Abstract

Plasmid pMQ3, carrying thedam gene ofEscherichia coli on a 6.1 Kb fragment, shows a tenfold increase in relative DNA adenine methylase activity, while plasmid pdam118, with a 1.14 Kbdam insert, shows only a twofold increase, although both plasmids were derived from plasmid pLC13–42. Since a copy number effect did not seem to be the cause of this difference, we have subcloned pMQ3 in order to determine whether the additional chromosomal DNA present in this plasmid is responsible for the enhancement of methylase activity. We show that the 346 base pairs upstream ofdam contain sequences necessary for expression. DNA sequence analysis has revealed that in pdam118 only the 118 bases 5-prime to thedam gene are present in other constructs and that the additional upstream material is pBR322 DNA. This shows that pdam118 carries a DNA duplication.

Keywords

Methylation Base Pair Adenine Twofold Increase Number Effect 

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Copyright information

© Springer-Verlag New York Inc. 1990

Authors and Affiliations

  • Judy A. Arraj
    • 1
  • Te-Hui Wu
    • 1
  • M. G. Marinus
    • 1
  1. 1.Department of PharmacologyUniversity of Massachusetts Medical SchoolWorcesterUSA

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