The conserved translocase Tim17 prevents mitochondrial DNA loss.

Maintenance of an intact mitochondrial genome is essential for oxidative phosphorylation in all eukaryotes. Depletion of mitochondrial genome copy number can have severe pathological consequences due to loss of respiratory capacity. In Saccharomyces cerevisiae, several bifunctional metabolic enzymes have been shown to be required for mitochondrial DNA (mtDNA) maintenance.

Mitochondrial nucleoids undergo remodeling in response to metabolic cues.

Mitochondrial DNA is organized as a nucleoprotein complex called the nucleoid. Its major protein components have been identified in different organisms, but it is yet unknown whether nucleoids undergo any form of remodeling. Using an in organello ChIP-on-chip assay, we demonstrate that the DNA-bending protein Abf2 binds to most of the mitochondrial genome with a preference for GC-rich gene sequences.

SIT4 regulation of Mig1p-mediated catabolite repression in Saccharomyces cerevisiae.

E153 is a respiratory deficient mutant of Saccharomyces cerevisiae with a mutation in the active site of the Sit4p protein phosphatase. Measurements of mitochondrial respiration and cytochromes indicate that the mutation suppresses glucose repression. The escape from catabolite repression is accompanied by a marked reduction of the transcriptional repressor Mig1p.

Activation of the SPS amino acid-sensing pathway in Saccharomyces cerevisiae correlates with the phosphorylation state of a sensor component, Ptr3.

Cells of the budding yeast Saccharomyces cerevisiae sense extracellular amino acids and activate expression of amino acid permeases through the SPS-sensing pathway, which consists of Ssy1, an amino acid sensor on the plasma membrane, and two downstream factors, Ptr3 and Ssy5. Upon activation of SPS signaling, two transcription factors, Stp1 and Stp2, undergo Ssy5-dependent proteolytic processing that enables their nuclear translocation. Here we show that Ptr3 is a phosphoprotein whose hyperphosphorylation is increased by external amino acids and is dependent on Ssy1 but not on Ssy5.

Evolutionary tinkering with mitochondrial nucleoids.

Mitochondrial DNA (mtDNA) is organized in nucleoprotein particles called nucleoids. Each nucleoid, which is considered a heritable unit of mtDNA, might contain several copies of the mitochondrial genome and several different proteins. Some nucleoid-associated proteins, such as the high mobility group (HMG) box family, have well defined functions in mtDNA maintenance and packaging; others, such as Aco1 and IIv5, are bifunctional, fulfilling their roles in nucleoids in addition to well established metabolic functions.