Transcriptional lockdown during acute proteotoxic stress

Quantitative real-time in-cell imaging reveals heterogeneous clusters of proteins prior to condensation

“…To test this hypothesis, we investigated the effect of a p38 kinase inhibitor on the different clusters. P38 kinase has been shown to shuttle to the nucleus upon stress [41, 53]. To ascertain whether the p38 kinase inhibitor interferes with NELF cluster formation, we incubated living cells with the p38 inhibitor for 1 h and then added As 2 O 3 and observed the cells for 30 min under our HILO microscope.…”

Adaptive preservation of orphan ribosomal proteins in chaperone-stirred condensates

“…Sis1 and Hsp70 actively maintain the oRPs in a usable state in the condensates until rRNA production resumes and the RPs are incorporated into nascent ribosomes. Supporting this model, cells are known to repress rRNA production during stress (Sawarkar, 2022; Shore et al, 2021), and inhibition of rRNA production has been shown to lead to accumulation of oRPs and activation of the HSR in the absence of environmental stress (Albert et al, 2019; Tye et al, 2019). While the mechanism by which heat shock inhibits transcription is unclear, it is known to be independent of the HSR (Rawat et al, 2021).…”

“…Upon exposure to a broad range of environmental stressors, cells rapidly inactivate ribosome biogenesis by repressing transcription of rRNA and RP mRNAs (Gasch et al, 2000; Gasch and Werner-Washburne, 2002; Sawarkar, 2022; Shore et al, 2021). Limiting production of ribosomes limits proliferation (Warner, 1999), providing a general mechanism for cells to simultaneously slow growth during stress and free up resources to mount an adaptive response.…”

“…Most RPs translocate from the cytosol into the nucleolus, and specific karyopherins and dedicated chaperones known as escortins mediate their transport (Pillet et al, 2017). Transcription of rRNA and the mRNAs encoding RPs is coordinately regulated and rapidly repressed upon nutrient limitation or other environmental stressors such as heat shock (Gasch et al, 2000; Gasch and Werner-Washburne, 2002; Sawarkar, 2022; Shore et al, 2021). However, while this transcriptional attenuation occurs even under modest stress conditions in yeast such as 37ºC, protein synthesis remains active and is only repressed at temperatures above 40ºC (Iserman et al, 2020; Muhlhofer et al, 2019).…”

Ring stage dormancy of Plasmodium falciparum tolerant to artemisinin and its analogues – A genetically regulated “Sleeping Beauty”

“…Prevention of non-ribosome-bound mRNAs from degradation by RNases is achieved by accumulating these untranslated transcripts into so-called stress granules. At the same time, gene expression enters into a stress-induced transcriptional attenuation, involving inhibition of transcription of a multitude of genes and up-regulation of a few stress-response genes to ameliorate damages and also in preparation for return to normalcy once the crisis has passed ( Sawarkar, 2022 ). This is reminiscent of the dormancy state observed with ring-stage ART-tolerant parasites in face of ART exposure in vitro , in which ring stage parasites of several Plasmodium falciparum lines were exposed to different doses of dihydroartemisinin (DHA), producing an abrupt arrest in parasite development after a single exposure to DHA, followed by recovery over a period of several days ( Teuscher et al, 2010 ).…”