Mitochondrial autonomy

In view of die mitochondrial autonomy and the existence of cell division independent neobiogenesis of these organelles it seems likely that in some respect mitochondrial ADP-ribosylation plays a role similar to that of nuclear ADP-ribosylation. There seems to exist certain links between ADP-ribosylation and mitochondrial replication. Our preliminary experiments showing an increase of ADP-ribosyl transferase activity during mitochondrial neobiogenesis are in favor of an involvement of ADP-ribosylation in mitochondrial replication. The topographical association of a part (25%) of protein ADP-ribosylation and mitochondrial DNA polymerase activities does also suggest such a relationship (11). 

Since it appears by now well established that the mitochondrial rRNAs, and at least the bulk of its tRNAs, are distinct from the species found in the cytosol, both in their nature and in their mode of specification by being mitochondrial transcripts (for reviews see introduction), we have recently concentrated our attention on mitochondrial mRNA. This species is, of course, of the greatest interest, not only because of its intrinsic importance to problems of mitochondrial autonomy, but also because the possibility of its nuclear origin and import into the mitochondria has been explicitly raised by several investigators. We have tried to obtain an answer to this question by means of the following paradigm. Three possible models can be envisaged ... 

Bosmann, H. B., and Martin, S. S., 1969, Mitochondrial autonomy, incorporation of monosaccharides into glycoprotein by isolated mitochondria. Science 164 190. 

Our group at Indiana University has been participating in these efforts since 1963, using, as do many others in the field, the versatile, unicellular eukaryote, Saccharomyces cerevisiae (Baker s yeast)—an ascomycete—as our object of study. Throughout, our interests have been centered as much on the limits of the autonomy of its mitochondrial organelles in their own biosynthesis as on the process itself " on what mitochondria cannot do by and for themselves on what and how they depend on the rest of the cell and how this mutual interdependence is brought about and regulated. 

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