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Characterization of Vsr endonucleases from Neisseria meningitidis

Milena Bażlekowa1, Monika Adamczyk-Popławska1, Agnieszka Kwiatek1

  • 1Department of Virology, Institute of Microbiology, Faculty of Biology, University of Warsaw, Miecznikowa 1, 02-096 Warsaw, Poland.

Microbiology (Reading, England)
|July 13, 2017
PubMed

Insights

DNA methylation can cause mutations. The study investigates meningococcal C5-methyltransferases and their Very Short Patch (VSP) repair system, revealing broader substrate specificity for DNA repair enzymes.

Area of Science:

  • Molecular Biology
  • Genetics
  • Microbial Pathogenesis

Background:

  • DNA methylation is a fundamental biological process with implications for genome stability.
  • Deamination of 5-methylcytosine leads to C→T transitions, a common mutagenic event.
  • The Very Short Patch (VSP) repair system, involving Vsr endonuclease, corrects these mismatches in bacteria like Escherichia coli.

Purpose of the Study:

  • To investigate the mutagenic potential of Neisseria meningitidis C5-methyltransferases (M.NmeDI and M.NmeAI).
  • To characterize the Vsr endonucleases encoded by N. meningitidis and their substrate specificities.
  • To explore the broader role and substrate range of the VSP repair system in N. meningitidis.

Main Methods:

  • Analysis of meningococcal C5-methyltransferases for mutagenic activity.
  • Phylogenetic analysis of N. meningitidis Vsr endonucleases.
  • In vitro characterization of Vsr endonuclease activity on various DNA mismatches.
  • Site-directed mutagenesis to restore activity in a non-functional Vsr endonuclease.

Main Results:

  • Meningococcal C5-methyltransferases contribute to C→T transition mutations via 5-methylcytosine deamination.
  • N. meningitidis possesses two distinct types of Vsr endonucleases (type I and type II).
  • The type II Vsr endonuclease (V.Nme18VIP) efficiently repairs T:G mismatches.
  • A specific mutation (Tyr69 to His69) restored activity to the type I Vsr endonuclease (V.Nme18IIP).
  • Both active Vsr endonucleases recognized and digested T:T and U:G mispairs in addition to T:G mismatches.

Conclusions:

  • The VSP repair system in N. meningitidis exhibits broader substrate specificity than previously understood.
  • Meningococcal Vsr endonucleases can repair DNA lesions beyond those arising solely from 5-methylcytosine deamination.
  • This study expands the known functions of the VSP repair pathway in maintaining genome integrity.

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