RNA EDITING OF THE COL MESSENGER-RNA THROUGHOUT THE LIFE-CYCLE OF PHYSARUM-POLYCEPHALUM

Editing of RNA via the insertion, deletion or substitution of genetic information affects gene expression in a variety of systems. Previous characterization of the Physarum polycephalum cytochrome c oxidase sub unit I (coI) mRNA revealed that both nucleotide insertions and base su bstitutions occur during the maturation of this mitochondrial message. Both types of editing are known to be developmentally regulated in ot her systems, including mammals and trypanosomatids. Here we show that the coI mRNA present in Physarum mitochondria is edited via specific n ucleotide insertions and C to U conversions at every stage of the life cycle. Primer extension sequencing of the RNA indicates that this edi ting is both accurate and efficient. Using a sensitive RT-PCR assay to monitor the extent of editing at individual sites of C insertion, we estimate that greater than 98% of the steady-state amount of coI mRNA is edited throughout the Physarum developmental cycle.