The pathogenic fungus must overcome multiple stressors to cause disease in its human host. found in a variety of environmental niches worldwide. As a pathogen causes meningoencephalitis in immune compromised individuals which is estimated to result in ARQ 197 over 600 0 deaths annually (Park encounters a multitude of stresses including changes in pH nutrients O2/CO2 concentration and temperature which it must overcome in order to cause systemic disease (Brown (Perfect 2006 Proper responses to stress involve specific and rapid changes in gene expression. Changes in transcription following exposure to stressors have been a primary focus of the work dedicated to investigating stress adaptation and many important stress-response pathways have been delineated (Kraus coordinates temperature-dependent changes in mRNA degradation is unknown. Recent studies in demonstrate that mRNA synthesis and degradation are coupled via the interaction of nascent transcripts with the Rpb4p/7p heterodimer a dissociable subunit of the RNA Polymerase II holoenzyme ARQ 197 (Shalem et al. 2011 Dori-Bachash et al. 2011 Goler-Baron influence the ability of this fungus to grow at host-temperature including calcineurin Ras1 and PKC pathways (Odom orthologs of the mammalian 3-phosphoinositide-dependent kinase (Pdk1) Pkh1p and Pkh2p are involved in mRNA decay and the formation of P-bodies cytoplasmic mRNP complexes that mediate mRNA degradation and translational repression (Luo (Luo plays a pivotal role in stress tolerance and virulence (Chabrier-Rosello strain that is null for the Pkh1 ortholog Pkh2-02 (Chabrier-Rosello et al. 2012 Lee et al. 2012 but a role in mRNA degradation was not investigated. In the current study when transcription and degradation were uncoupled by deletion of the ortholog adaptation to host-temperature was impaired. RP transcripts ARQ 197 were transiently repressed during host-temperature adaptation in a Ccr4- and Rpb4-dependent manner. Concurrently the localization of Rpb4 changed in response to temperature stress resulting in reduced nuclear localization and punctate accumulation in the cytoplasm immediately following a temperature shift followed by movement back to the nucleus after longer exposure to the stress. Although Rpb4 does not appear to play a role in the stability of ER stress transcripts under unstressed conditions or at the onset of ER stress the accelerated degradation of these transcripts following peak induction of the ER Stress Response during host-temperature adaptation was Rpb4-dependent suggesting a role for Rpb4 in the regulation of stress response intensity and duration. Our ARQ 197 studies also revealed that enhanced degradation of RP transcripts but not ER stress transcripts CXXC9 was dependent on Pkh2-02 signaling but was independent of the downstream PKC1-MPK1 MAP kinase cascade. Finally when transcription and degradation were uncoupled by deletion of Rpb4 virulence was attenuated in a mouse model of disseminated cryptococcosis. Together these data demonstrate that coupling of transcription and mRNA degradation through Rpb4 plays a fundamental role in regulating gene expression and host-temperature adaptation. RESULTS RP transcripts undergo accelerated Ccr4-mediated degradation immediately following exposure to host-temperature In a microarray analyses that compared the wild type (H99) to a (CNAG_05232) and (CNAG_00779)during 1-hour time courses in which transcription was inhibited with 1 10 while cells remained incubated at 30°C (Fig. 1A) or were shifted to 37°C (Fig. 1B). When wild type cells were incubated under optimal conditions (30°C) the half-lives of and were 39 and 35 minutes among biological replicates respectively. When wild type ARQ 197 cells were shifted to 37°C we found that the half-lives of these transcripts were dramatically and significantly reduced to 18 minutes (< 0.001) and 19 minutes (< 0.01). In the < 0.001 0.01 37 and < 0.001) with half-lives >60 minutes at both temperatures (Fig. 1). These data demonstrate that RP transcripts are immediately destabilized in response to host-temperature and that the post-transcriptional regulation of RP transcripts requires Ccr4. Figure 1 Ccr4-mediated degradation of RP transcripts is enhanced following a shift to.