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Pseudoknot-dependent translational coupling in repBA genes of the IncB plasmid pMU720 involves reinitiation

J Praszkier1, A J Pittard

  • 1Department of Microbiology and Immunology, The University of Melbourne, Victoria 3010, Australia. judy@ariel.its.unimelb.edu.au

Journal of Bacteriology
|September 25, 2002
PubMed

Insights

Replication of miniplasmid pMU720 depends on coupled translation of RepB and RepA proteins. A pseudoknot structure and antisense RNAI regulate this process, ensuring proper plasmid replication and copy number control.

Area of Science:

  • Molecular Biology
  • Microbiology
  • Genetics

Background:

  • The IncB miniplasmid pMU720 requires the replication initiator protein RepA for its replication.
  • RepA translation is coupled to a leader peptide, RepB, forming the repBA operon.
  • Translational coupling in repBA is activated by a pseudoknot upstream of the repA Shine-Dalgarno sequence.

Purpose of the Study:

  • To investigate the mechanism of translational coupling in the repBA system.
  • To elucidate the role of the pseudoknot in repA translation and plasmid replication.
  • To understand how antisense RNAI controls plasmid copy number.

Main Methods:

  • Utilized a specialized ribosome system with altered anti-Shine-Dalgarno sequences.
  • Analyzed mRNA molecules with complementary Shine-Dalgarno sequences.
  • Investigated the interaction between RNAI and repBA mRNA.

Main Results:

  • Data suggest that repA translation is initiated by reinitiation of ribosomes terminating repB translation.
  • The pseudoknot structure is crucial for activating repA translation.
  • Antisense RNAI inhibits repA expression by preventing pseudoknot formation and inhibiting RepB translation.

Conclusions:

  • Ribosome reinitiation is the mechanism for coupled translation of repBA.
  • The pseudoknot plays a key role in translational coupling and copy number control of pMU720.
  • RNAI acts as a negative regulator, controlling plasmid replication through modulation of repBA expression.

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