Nab3 nuclear granule accumulation is driven by respiratory capacity

• Type of Material: Article
• Authors: Katherine M Hutchinson, Emory University; Jeremy C Hunn, Emory University; Daniel Reines, Emory University
• Language: English
• Date: 2022-08-03
• Publisher: SPRINGER
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature
• Final Published Version (URL): http://dx.doi.org/10.1007/s00294-022-01248-w
• Title of Journal or Parent Work: CURRENT GENETICS
• Volume: 68
• Issue: 5-6
• Start Page: 581
• End Page: 591
• Grant/Funding Information: This work was funded by National Institutes of Health (R01 GM120271 to D.R.), the Emory University School of Medicine, the Emory University Research Committee, and the Emory Integrated Cellular Imaging Core. The content is solely the responsibility of the authors and does not necessarily reflect the official views of the National Institute of Health.
• Keywords: Science & Technology; BUDDING YEAST; Nab3; START-SITE SELECTION; GENE; IMD2 TRANSCRIPTION; Low complexity domain; Mitochondria; STRESS GRANULES; Life Sciences & Biomedicine; PHENOTYPE; KINASE; Yeast; Genetics & Heredity; Granule; TERMINATION

Abstract

Numerous biological processes involve proteins capable of transiently assembling into subcellular compartments necessary for cellular functions. One process is the RNA polymerase II transcription cycle which involves initiation, elongation, co-transcriptional modification of nascent RNA, and termination. The essential yeast transcription termination factor Nab3 is required for termination of small non-coding RNAs and accumulates into a compact nuclear granule upon glucose removal. Nab3 nuclear granule accumulation varies in penetrance across yeast strains and a higher Nab3 granule accumulation phenotype is associated with petite strains, suggesting a possible ATP-dependent mechanism for granule disassembly. Here, we demonstrate the uncoupling of mitochondrial oxidative phosphorylation by drug treatment or deletions of nuclear-encoded ATP synthase subunit genes were sufficient to increase Nab3 granule accumulation and led to an inability to proliferate during prolonged glucose deprivation, which requires respiration. Additionally, by enriching for respiration competent cells from a petite-prone strain, we generated a low granule-accumulating strain from a relatively high one, providing another link between respiratory competency and Nab3 granules. Consistent with the resulting idea that ATP is involved in granule accumulation, the addition of extracellular ATP to semi-permeabilized cells was sufficient to reduce Nab3 granule accumulation. Deleting the SKY1 gene, which encodes a kinase that phosphorylates nuclear SR repeat-containing proteins and is involved in efficient stress granule disassembly, also resulted in increased granule accumulation. This observation implicates Sky1 in Nab3 granule biogenesis. Taken together, these findings suggest there is normally an equilibrium between termination factor granule assembly and disassembly mediated by ATP-requiring nuclear machinery.