DNA polymerase I is an efficient reverse transcriptase that mediates RNA-templated DNA repair synthesis

Area of Science:

• Molecular Biology
• Genomics
• Biochemistry

Background:

• Ribonucleotides are frequently incorporated into genomic DNA during normal growth and stress.
• The specific DNA polymerase responsible for RNA-templated DNA synthesis remains unidentified.

Purpose of the Study:

• To identify the bacterial DNA polymerase catalyzing RNA-dependent DNA synthesis.
• To characterize the reverse transcriptase activity of bacterial DNA polymerase I (Pol I).

Main Methods:

• Testing various bacterial Pol I enzymes for reverse transcriptase (RT) activity.
• Comparing the RNA-dependent DNA synthesis activity of *B. subtilis* Pol I with a known reverse transcriptase.
• Assessing the ability of Pol I and replicative DNA polymerase PolC to navigate RNA embedded within DNA templates.

Main Results:

• All tested bacterial Pol I enzymes exhibited reverse transcriptase activity.
• *B. subtilis* Pol I demonstrated RNA-dependent DNA synthesis comparable to Moloney Murine Leukemia Virus reverse transcriptase.
• Pol I efficiently processed long stretches of templated ribonucleotides, whereas PolC arrested at single ribonucleotides.

Conclusions:

• Bacterial DNA polymerase I is a robust reverse transcriptase.
• Pol I facilitates RNA-templated DNA replication, enabling replication forks to overcome persistent RNA in genomic DNA.