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Cytosine methylation of the sequence GATC in a mycoplasma
Abstract:
Mycoplasma virus L2 is subject to host-specific restriction and modification in Acholeplasma laidlawii strains JA1 and K2. We have examined the DNAs from both host cells and viruses propagated on these strains with respect to susceptibility to cleavage by restriction endonucleases and for DNA base modifications. We show that, in strain K2 and L2 virus grown on K2 cells, cytosine in the sequence GATC is methylated to 5-methylcytosine and, although strain K2 and L2 viruses grown on K2 contain N6-methyladenine in their DNA, adenine in the sequence GATC is not methylated. In contrast to K2, strain JA1 and L2 virus grown on JA1 cells contain no detectable methylated bases. It is not known which of the methylated bases in K2 is the basis for the K2 restriction-modification system operative on L2 virus.
Insights
Mycoplasma virus L2 DNA undergoes host-specific modification in Acholeplasma laidlawii. Strain K2 methylates cytosine, while strain JA1 shows no detectable DNA base modifications, impacting virus infectivity.
Area of Science:
- Microbiology
- Molecular Biology
- Virology
Background:
- Mycoplasma virus L2 exhibits host-specific restriction and modification.
- Acholeplasma laidlawii strains JA1 and K2 possess distinct modification systems.
Purpose of the Study:
- To investigate DNA base modifications in Acholeplasma laidlawii strains JA1 and K2.
- To understand the molecular basis of host-specific restriction and modification of Mycoplasma virus L2.
Main Methods:
- Analysis of host cell and viral DNA susceptibility to restriction endonucleases.
- DNA base modification analysis using biochemical methods.
Main Results:
- Strain K2 and Mycoplasma virus L2 grown on K2 cells show cytosine methylation at the GATC sequence (5-methylcytosine).
- N6-methyladenine is present in K2-grown virus DNA, but adenine in the GATC sequence is not methylated.
- Strain JA1 and Mycoplasma virus L2 grown on JA1 cells lack detectable methylated bases.
Conclusions:
- Acholeplasma laidlawii strain K2 employs cytosine methylation as part of its restriction-modification system for Mycoplasma virus L2.
- The specific methylated base responsible for K2 restriction-modification remains to be identified.