Figure 2.

rNMPs incorporation and removal from mitochondrial and chloroplast DNA. Single and multiple ribonucleotides found into the DNA of mitochondria and chloroplasts may result from different sources. Several DNA polymerases might contribute to the incorporation of rNMPs, as demonstrated for pol γ acting on mtDNA. The activity of RNase H1 is essential for processing polyribonucleotide chains synthesized for replication priming, while single rNMPs remain unprocessed due to the absence of RNase H2.