Processing of precursor RNAs from mitochondria ofNeurospora crassa

Neurospora mitochondrial DNA is transcribed into long molecules containing the information of several genes. Processing leads to formation of functionally active RNAs. It has been shown previously that when tRNA sequences are present in these transcripts excision of mRNAs occurs at the acceptor stem of these tRNA sequences. We have investigated the processing of precursor RNAs transcribed from a region of the mitochondrial genome devoid of tRNA genes. This region comprises the genes encoding subunit 6 of the mitochondrial ATPase, subunit 2 of cytochrome aa3 and a mitochondrial ATPase proteolipid-like gene. We have proved that a common precursor of the putative mRNAs of these genes exists and we have determined the positions of the 5' and 3' ends of processing intermediates and of the mature mRNAs. We will discuss possible processing routes and secondary structures that substitute for tRNA sequences as processing sites.