Poster abstracts

Poster number 102 submitted by David Goich

Crosstalk and compensation between the Hog1 and Gcn2 pathways in C. neoformans stress adaptation.

David Goich (SUNY Buffalo, Department of Microbiology and Immunology), Amanda LM Bloom (SUNY Buffalo, Department of Microbiology and Immunology), Murat C Kalem (SUNY Buffalo, Department of Microbiology and Immunology), John C Panepinto (SUNY Buffalo, Department of Microbiology and Immunology)

Abstract:
Cryptococcus neoformans is an environmental fungus that causes severe opportunistic infections in immunocompromised individuals, particularly people living with HIV/AIDS. Upon entry into the host, C. neoformans rapidly alters its proteome to accommodate a variety of stressors, including elevated temperature, reactive oxygen species (ROS) in phagocytes, nutrient limitation, and more. Our previous work demonstrated that these processes are dependent in part on the p38 MAPK, Hog1, which couples the translational response to stress-sensing signal transduction. Our preliminary data found that signaling via the Gcn2 pathway, another stress-induced repressor of translation, is upregulated in a hog1∆ mutant strain. We generated a hog1gcn2∆∆ strain to investigate whether defects in translation regulation in hog1∆ are a result of, or masked by, hyperactivity of the Gcn2 pathway. First, we investigated whether loss of both kinases resulted in exacerbated growth defects under thermal and oxidative stresses, measured by spot dilution assays and kinetic growth curves. Using polysome profiling and northern blots, we also investigated whether loss of both kinases resulted in synergistic defects in global translation and repression of homeostatic mRNAs during stress. Lastly, we used RNA-seq to investigate whether the Gcn2-dependent transcriptional response was enhanced in hog1∆. Compared to either single knockout, we found that hog1gcn2∆∆ had exacerbated growth defects under thermal and oxidative stress, and that this was associated with defects in both global translation and repression of homeostatic transcripts. Surprisingly, hyperactivity of the Gcn2 pathway in hog1∆ led to enhanced transcriptional response in the context of thermal, but not oxidative stress. Our data suggest that crosstalk between Hog1 and Gcn2 is compensatory or redundant in regulation of translation and mRNA decay, but that the coupling of this crosstalk to transcription is stress-specific. Ongoing investigations will determine whether transcriptional and translational defects of hog1gcn2∆∆ are associated with attenuated virulence.

Keywords: translation, transcriptome, signaling