Dynamics of packaging and division of the yeast mitochondrial nuclei.

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Morphological and biochemical approaches were performed on the mechanisms of packaging and division of yeast mitochondrial nuclei (mt-nuclei).1. Dynamic changes in mt-nuclei during the transition from anaerobic to aerobic culture were investigated in the yeast Saccharomyces cerevisiae. During transition of the culture, the mt-nuclei changes their morphology from giant aggregates to small particles within 6 h. In the present study, we determined DNA content of individual giant mt-nuclei and small mt-nuclei. Next, we found that two species of mt-nuclei proteins were hardly detected in giant mt-nuclei in anaerobically-grown cells, but both proteins appeared in the small mt-nuclei during transfer to aerobic conditions. Using immnofluorescence microscopy, we demonstrated that the dynamic morphological changes in mitochondria occur parallel to the changes of the mt-nuclei and that the actin patches in the cytoplasm also changes from the aggregated forms to the small patches in response to th … More e aerobic conditions.2. Roles of protein components on packaging of the mt-nuclei were investigated, and following results were obtained.We identified a novel mt-nuclei protein named as Mnp1p. This protein was a 22-kDa acidic protein and had a homology with E. coli ribosomal protein, L7/L12. In order to examine the diversity of the mt-nuclei proteins from evolutionary aspects, we isolated the mt-nuclei from the yeast Candida parapsilosis and identified several mt-nuclei proteins. Furthermore, we purified a novel 30-kDa DNA-binding protein, a putative Abf2p homolog. We also successfully purified a 26-kDa Abf2p-like protein from the yeast Pichia jadinii.3. Nuclease sensitivity of the mt-nuclei was compared between mt-nuclei from wild-type cells and Abf2p-deficient cells. We found that the mt-nuclei from Abf2p-deficient cells were more resistant to micrococcal nuclease digestion than the mt-nuclei from wild type cells. During the course of study, we demonstrated that a major nuclease associated with mt-nuclei is a Nuc1p nuclease. MtDNA that is packaged into the mt-nuclei was digested uniformly rather than discontinuously with micrococcal nuclease. Less