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Bacteriophage lambda DNA fragments replicate in the Paramecium macronucleus: absence of active copy number control

C S Kim1, J R Preer, B Polisky

  • 1Department of Biology, Indiana University, Bloomington 47405.

Developmental Genetics
|January 11, 1992
PubMed

Insights

Bacteriophage lambda DNA fragments microinjected into Paramecium replicate as linear molecules, acquiring Paramecium telomeres. These DNA fragments are not actively copy-controlled, replicating once per cell division.

Area of Science:

  • Molecular Biology
  • Genetics
  • Protozoology

Background:

  • Bacteriophage lambda DNA is a well-characterized viral genome.
  • Paramecium is a ciliated protozoan with a complex nuclear dimorphism.
  • Telomeres are crucial for chromosome stability.

Purpose of the Study:

  • To investigate the replication and maintenance of bacteriophage lambda DNA fragments microinjected into Paramecium macronuclei.
  • To determine if exogenous DNA can be processed and maintained within the Paramecium macronuclear environment.
  • To understand the copy number control mechanisms for foreign DNA in Paramecium.

Main Methods:

  • Microinjection of bacteriophage lambda DNA fragments into Paramecium macronuclei.
  • Analysis of DNA replication and integration using molecular techniques.
  • Assessment of DNA copy number over multiple cell divisions (fissions).
  • Investigation of telomere addition to the linear DNA fragments.

Main Results:

  • Microinjected bacteriophage lambda DNA fragments replicate as unit-length linear molecules within the Paramecium macronucleus.
  • These linear DNA molecules serve as substrates for the addition of Paramecium telomeres by endogenous telomerase.
  • The copy number of injected DNA can reach levels higher than endogenous chromosomes and is not actively controlled.
  • The copy number after multiple fissions correlates with the initial input copy number, suggesting replication occurs once per cell division.

Conclusions:

  • Exogenous linear DNA can be replicated and stabilized in the Paramecium macronucleus.
  • Paramecium telomerase can process and add telomeres to foreign DNA substrates.
  • The Paramecium macronucleus lacks active copy number control for this type of injected DNA, with replication occurring once per cell cycle.

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