The highly compact structure of the mitochondrial DNA polymerase genomic region of Drosophila melanogaster: functional and evolutionary implications.

The structure of a Drosophila melanogaster genomic region containing five tightly clustered genes has been determined and evaluated with regard to its functional and evolutionary relationships. In addition to the genes encoding the two subunits (alpha and beta) of the DNA polymerase gamma holoenzyme, the key enzyme for mitochondrial DNA replication, other genes contained in the cluster may be also involved in the cellular distribution of mitochondria and in the coordination of mitochondrial and nuclear DNA replication. The gene cluster is extremely compact, with very little intergenic space. It contains two bidirectional promoter regions, and particularly notable is the 5' end overlap detected in two of its genes, an exceptional situation in both prokaryotic and eukaryotic genome organization.