DNA packaging proteins Glom and Glom2 coordinately organize the mitochondrial nucleoid of Physarum polycephalum

Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Aichi 464-8602, Japan.
Mitochondrion (Impact Factor: 3.52). 03/2011; 11(4):575-86. DOI: 10.1016/j.mito.2011.03.002
Source: PubMed

ABSTRACT Mitochondrial DNA (mtDNA) is generally packaged into the mitochondrial nucleoid (mt-nucleoid) by a high-mobility group (HMG) protein. Glom is an mtDNA-packaging HMG protein in Physarum polycephalum. Here we identified a new mtDNA-packaging protein, Glom2, which had a region homologous with yeast Mgm101. Glom2 could bind to an entire mtDNA and worked synergistically with Glom for condensation of mtDNA in vitro. Down-regulation of Glom2 enhanced the alteration of mt-nucleoid morphology and the loss of mtDNA induced by down-regulation of Glom, and impaired mRNA accumulation of some mtDNA-encoded genes. These data suggest that Glom2 may organize the mt-nucleoid coordinately with Glom.

Download full-text


Available from: Mamoru Sugita, Jun 21, 2015
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The mitochondrial genome maintenance gene, MGM101, is essential for yeasts that depend on mitochondrial DNA replication. Previously, in Saccharomyces cerevisiae, it has been found that the carboxy-terminal two-thirds of Mgm101p has a functional core. Furthermore, there is a high level of amino acid sequence conservation in this region from widely diverse species. By contrast, the amino-terminal region, that is also essential for function, does not have recognizable conservation. Using a bioinformatic approach we find that the functional core from yeast and a corresponding region of Mgm101p from the coral Acropora millepora have an ordered structure, while the N-terminal domains of sequences from yeast and coral are predicted to be disordered. To examine whether ordered and disordered domains of Mgm101p have specific or general functions we made chimeric proteins from yeast and coral by swapping the two regions. We find, by an in vivo assay in S.cerevisiae, that the ordered domain of A.millepora can functionally replace the yeast core region but the disordered domain of the coral protein cannot substitute for its yeast counterpart. Mgm101p is found in the mitochondrial nucleoid along with enzymes and proteins involved in mtDNA replication. By attaching green fluorescent protein to the N-terminal disordered domain of yeast Mgm101p we find that GFP is still directed to the mitochondrial nucleoid where full-length Mgm101p-GFP is targeted.
    PLoS ONE 02/2013; 8(2):e56465. DOI:10.1371/journal.pone.0056465 · 3.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Mitochondrial DNA (mtDNA) is highly compacted into DNA-protein structures termed mitochondrial nucleoids (mt-nucleoids). The key mt-nucleoid components responsible for mtDNA condensation are HMG-box containing proteins such as mammalian mitochondrial transcription factor A (TFAM) and Abf2p of the yeast Saccharomyces cerevisiae. To gain insight into function and organization of mt-nucleoids in strictly aerobic organisms, we initiated studies of these DNA-protein structures in Yarrowia lipolytica. We identified a principal component of mt-nucleoids in this yeast and termed it YlMhb1p (Y. lipolytica Mitochondrial HMG-box containing protein 1). It contains two putative HMG-boxes contributing to both DNA-binding and its ability to compact mtDNA in vitro. A phenotypic analysis of a Δmhb1 strain lacking YlMhb1p resulted in three interesting findings. First, although the mutant exhibits clear differences in mt-nucleoids accompanied by a large decrease in mtDNA copy number and mtDNA-derived transcripts, its respiratory characteristics and growth at most of the tested conditions are indistinguishable from the wild-type strain. Second, our results indicate that a potential imbalance between subunits of the respiratory chain encoded separately by nuclear and mtDNA is prevented at a (post)translational level. Third, we found that mtDNA in the Δmhb1 strain is more prone to mutations, indicating that mtHMG-box containing proteins protect mitochondrial genome against mutagenic events.
    Eukaryotic Cell 06/2014; 13(9). DOI:10.1128/EC.00092-14 · 3.18 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: SUMMARY Homologous recombination is a universal process, conserved from bacteriophage to human, which is important for the repair of double-strand DNA breaks. Recombination in mitochondrial DNA (mtDNA) was documented more than 4 decades ago, but the underlying molecular mechanism has remained elusive. Recent studies have revealed the presence of a Rad52-type recombination system of bacteriophage origin in mitochondria, which operates by a single-strand annealing mechanism independent of the canonical RecA/Rad51-type recombinases. Increasing evidence supports the notion that, like in bacteriophages, mtDNA inheritance is a coordinated interplay between recombination, repair, and replication. These findings could have profound implications for understanding the mechanism of mtDNA inheritance and the generation of mtDNA deletions in aging cells.
    Microbiology and molecular biology reviews: MMBR 09/2013; 77(3):476-96. DOI:10.1128/MMBR.00007-13 · 15.26 Impact Factor