Cleavage of host tRNAs by mycoplasma membrane-associated nuclease

Area of Science:

• Microbiology
• Molecular Biology
• Cell Biology

Background:

• Mycoplasmas are significant pathogens and common cell culture contaminants.
• The precise mechanisms by which mycoplasma nucleases affect host cell RNA metabolism remain largely unknown.

Purpose of the Study:

• To investigate the impact of Mycoplasma hyorhinis nucleases on host cell RNAs.
• To identify the specific mycoplasma factor responsible for RNA cleavage.

Main Methods:

• Infection of host cells with Mycoplasma hyorhinis.
• Analysis of host cell RNA cleavage upon cell scraping and lysis.
• Identification and purification of the responsible nuclease (MnuA).
• Biochemical characterization of MnuA's enzymatic activities (DNase and RNase).
• Mutational analysis of the MnuA protein.

Main Results:

• Mycoplasma hyorhinis infection induces significant cleavage of host cell transfer RNAs (tRNAs).
• The membrane-associated nuclease A (MnuA) protein is identified as the key factor responsible for this tRNA cleavage.
• MnuA exhibits both DNase and RNase activities, with a specific preference for tRNAs in live cells.
• MnuA's nuclease activity is mediated by a domain similar to DNase I.
• M. hyorhinis infection exacerbates tRNA cleavage under conditions of amino acid deprivation.

Conclusions:

• Mycoplasma hyorhinis utilizes MnuA to cleave host cell tRNAs, impacting host RNA metabolism.
• The findings highlight a novel mechanism by which mycoplasma contaminants can disrupt host cell function.
• Conserved mnuA genes across mycoplasma species suggest this mechanism is widespread.