Mapping of the ARS-like activity and transcription initiation sites in the non-canonical yeast mitochondrial ori 6 region.

The insert-containing, non-canonical ori 6 region of yeast mitochondrial DNA of Saccharomyces cerevisiae was dissected into 15 different segments that were ligated to the integrative yeast vector YIp5. Six recombinant plasmids exhibited replicative ability in yeast and carried consensus sequences similar to the previously described 11 bp motifs active as autonomous replication sequences (ARS). In addition, all active constructions carry one or more of the characteristic GC-rich domains A, B or C present in the ori 6 region, thus confirming and expanding the study of Blanc (Gene 30 (1984) 47-61) with the canonical ori 5. Also a new transcriptional origin is activated in the ori 6 region, apparently circumventing a disruption by insertion of a GC-rich sequence that, in this ori, removes the mitochondrial promoter usually present next to the C element. The ARS-positive constructions correspond to the retained segments of spontaneous well-characterized suppressive or neutral petite genomes that contain segments of the ori sequence.