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Characterization of the intergenic region which regulates the MspI restriction-modification system

S Som1, S Friedman

  • 1Department of Pharmacology, State University of New York Health Science Center, Brooklyn 11203, USA.

Journal of Bacteriology
|February 1, 1997
PubMed

Insights

The MspI modification enzyme (M.MspI) represses its own gene (mspIM) expression by binding to DNA, but not the restriction enzyme gene (mspIR). This DNA-binding mechanism regulates MspI enzyme production.

Area of Science:

  • Molecular Biology
  • Genetics
  • Enzymology

Background:

  • The MspI restriction-modification system involves two genes: mspIM for the modification enzyme (M.MspI) and mspIR for the restriction enzyme (R.MspI).
  • Understanding the regulation of these genes is crucial for comprehending DNA methylation and restriction processes.

Purpose of the Study:

  • To investigate the regulatory mechanisms controlling the expression of mspIM and mspIR genes.
  • To determine the role of the M.MspI enzyme in the regulation of its own gene and the mspIR gene.

Main Methods:

  • Fusion of the intergenic region between mspIM and mspIR with lacZ in both orientations.
  • Analysis of gene expression levels using lacZ reporter assays.
  • Identification of transcription start sites.
  • DNase I footprinting to map M.MspI DNA-binding sites.

Main Results:

  • Expression of mspIM-lacZ fusion was over 400-fold higher than mspIR-lacZ fusion.
  • M.MspI repressed mspIM-lacZ expression in trans by binding to DNA.
  • M.MspI did not affect mspIR-lacZ expression.
  • DNase I footprinting identified M.MspI binding site within the mspIM regulatory elements.

Conclusions:

  • M.MspI autorepresses its own gene expression through specific DNA binding.
  • The mspIR gene is not regulated by M.MspI.
  • The intergenic region contains distinct regulatory elements for mspIM and mspIR.

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