Reducing Ribosome Biosynthesis Promotes Translation during Low Mg2+ Stress

• Published in: Molecular cell Vol. 64; no. 3; pp. 480 - 492
• Main Authors: Pontes, Mauricio H., Yeom, Jinki, Groisman, Eduardo A.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 03.11.2016
• ISSN: 1097-2765; 1097-4164
• DOI: 10.1016/j.molcel.2016.05.008

The synthesis of ribosomes is regulated by both amino acid abundance and the availability of ATP, which regenerates guanosine triphosphate (GTP), powers ribosomes, and promotes transcription of rRNA genes. We now report that bacteria supersede both of these controls when experiencing low cytosolic magnesium (Mg2+), a divalent cation essential for ribosome stabilization and for neutralization of ATP’s negative charge. We uncover a regulatory circuit that responds to low cytosolic Mg2+ by promoting expression of proteins that import Mg2+ and lower ATP amounts. This response reduces the levels of ATP and ribosomes, making Mg2+ ions available for translation. Mutants defective in Mg2+ uptake and unable to reduce ATP levels accumulate non-functional ribosomal components and undergo translational arrest. Our findings establish a paradigm whereby cells reduce the amounts of translating ribosomes to carry out protein synthesis. [Display omitted] •Low cytosolic Mg2+ promotes Mg2+ importation and reduction of ATP levels•A reduction in ATP levels frees Mg2+ and reduces ribosome production•Freed cytosolic Mg2+ enables ribosome assembly, allowing translation to continue Bacteria respond to low Mg2+ stress by promoting Mg2+ uptake and decreasing ATP levels. This response enables protein synthesis to continue with a decreased ribosome pool.