Nab3 nuclear granule accumulation is driven by respiratory capacity.

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Proteins transiently assemble into subcellular compartments for cellular functions.
• The RNA polymerase II transcription cycle involves multiple stages, including transcription termination.
• The yeast transcription termination factor Nab3 forms nuclear granules upon glucose removal, with accumulation varying by strain.

Purpose of the Study:

• To investigate the mechanism of Nab3 nuclear granule accumulation and disassembly.
• To explore the role of ATP and respiratory competency in Nab3 granule formation.
• To identify factors involved in regulating Nab3 granule dynamics.

Main Methods:

• Uncoupling mitochondrial oxidative phosphorylation using drug treatment or gene deletions.
• Assessing Nab3 granule accumulation in yeast strains with altered respiratory function.
• Evaluating the effect of extracellular ATP on Nab3 granule formation in semi-permeabilized cells.
• Investigating the role of the SKY1 gene in Nab3 granule dynamics through gene deletion.

Main Results:

• Disrupting mitochondrial oxidative phosphorylation increased Nab3 granule accumulation and impaired proliferation during glucose deprivation.
• Enriching for respiratory competent cells reduced Nab3 granule accumulation.
• Extracellular ATP addition decreased Nab3 granule accumulation.
• Deleting the SKY1 gene resulted in increased Nab3 granule accumulation.

Conclusions:

• Nab3 nuclear granule accumulation is linked to impaired respiratory function and potentially ATP levels.
• ATP-dependent nuclear machinery and the Sky1 kinase are involved in the disassembly of Nab3 granules.
• An equilibrium between Nab3 granule assembly and disassembly, mediated by ATP-requiring processes, is essential for cellular function.