DNA Double-strand Break in vivo at the 3′ Extremity of Exons Located Upstream of Group II Introns

In the filamentous fungus Podospora anserina, the unavoidable phenomenon of senescence is associated with the amplification of the first intron of the mitochondrial cox1 that accumulates as circular DNA molecules consisting of tandem repeats. This group II intron (cox1-i1 or α) is able to transpose and contains an open reading frame with significant amino acid similarity with reverse transcriptases. The generation of these intronic circular DNA...