Transfer RNA Abundance Alters Modification Levels in Response to Peroxide Stress in the Radiation Resistant Fungus Cryptococcus neoformans

Abstract

Cryptococcus neoformans is a radiation resistant fungus that has been found growing at the site of the nuclear reactor meltdown in Chernobyl, Ukraine. The Defense Threat Reduction Agency (DTRA) funds research on this organism to gain fundamental knowledge on radiation survival. Many DTRA projects cause soldiers to be exposed to radiation, therefore, gaining this information may have future therapeutic implications. Radiation causes cellular damage through the radiolysis of water into reactive oxygen species (ROS) – such as hydrogen peroxide. Cells have mechanisms such as antioxidants to regulate ROS levels. When ROS is too high, nucleic acids may be damaged. Transfer RNA (tRNA) – the molecule that carries the amino acid to the translational machinery – directly affect protein production. Hence, the integrity of tRNA is critical to antioxidant defenses and general protein synthesis. Chemical modifications to tRNA are abundant and crucial in all domains of life. Peroxide is known to cause changes in tRNA modification 5‐methylcytidine (m5C) levels in the model fungus S. cerevisiae. This work sets out to evaluate the effects of peroxide exposure on tRNA modification and tRNA transcript abundance in C. neoformans. Using liquid chromatography coupled with mass spectrometry (LC‐MS), modifications were relatively quantified and found to respond differently than in S. cerevisiae. Moreover, RNA sequencing information indicated that there are changes in tRNA abundance in response to peroxide. Since the modifying enzyme transcripts were not altered, the tRNA transcript abundance was reflected in the detected modification levels. Therefore, C. neoformans exhibits an increase in certain tRNA transcripts which then causes an increase in those tRNAs’ modifications. In conclusion, C. neoformans responds to peroxide stress via regulation of the tRNA pool – consequently altering the modifications within it.Support or Funding InformationThis work was funded by the Defense Threat Reduction Agency (DTRA) ‐ a branch of the US Department of Defense (DoD). Further support has been provided by the University of Cincinnati.