Translational Control of Conidial Germination in Aspergillus fumigatus

PROJECT SUMMARY/ABSTRACT Aspergillus fumigatus is a major human fungal pathogen capable of causing a range of diseases, including invasive pulmonary aspergillosis and disseminated aspergillosis in a wide variety of immunocompromised individuals, including organ transplant recipients and cancer patients. Mortality rates are as high as 40-50% in

these patients and direct healthcare costs associated with invasive aspergillosis, $4.6 billion in the U.S., are more than those of any other fungal infection. A. fumigatus, normally found in the soil and environment, produces asexual conidia that are typically inhaled in the lungs. Under appropriate host environmental

conditions conidia will germinate and eventually form hyphae that can not only penetrate lung tissue but also establish a disseminated bloodstream infection. Conidial germination is thus critical for A. fumigatus virulence and pathogenesis. While a variety of post-translational and transcriptional regulators are known to play

important roles in conidial germination, very little, if anything, is known about translational mechanisms. However, multiple lines of evidence suggest that translational regulation plays an important role, including the demonstration that conidial germination can be abrogated by inhibitors of translation, but not RNA or DNA

synthesis, that dormant conidia harbor a significant number of stored transcripts, which are primed for rapid translation and activation, and that translation is one of the earliest detectable events in germinating conidia. In addition, a comparative proteomic and transcriptomic study indicated that many genes show significant

differences in transcript vs. protein expression changes during A. fumigatus conidial germination and transcripts of several key regulators of this process possess unusually long 5’ UTR regions, which have been associated with translational regulation of morphology and other virulence processes in the human fungal

pathogen Candida albicans. We have also recently used ribosome profiling to demonstrate that the C. albicans yeast-hyphal morphological transition, which is similar to A. fumigatus germination/polarized growth, is under widespread global translational regulation that does not simply parallel transcriptional regulation; many genes

associated with virulence and virulence-related processes show altered translational efficiency. Based on this evidence, we hypothesize that translational mechanisms play an important role in controlling A. fumigatus conidial germination, distinct from that of transcriptional mechanisms, which will reveal novel potential

antifungal targets. In order to test this hypothesis, we will: 1) determine the global translational profile of A. fumigatus during conidial germination, 2) identify and characterize translational mechanisms important for A. fumigatus conidial germination. Ultimately, this study will provide a better understanding of global regulatory

circuits and pathways controlling A. fumigatus conidial germination at the translational level. This study will also identify and characterize several key translationally regulated factors important for A. fumigatus conidial germination that could potentially serve as targets for novel and more effective antifungals.