New Study Reveals Molecular Mechanism Behind DNA Repair Pathway

New research published in Cell unveils a molecular mechanism behind a DNA repair pathway that addresses the inclusion of ribonucleotides into genetic codes. The study, led by Evgeny Nudler and his team at NYU Langone Health, highlights the role of RNA polymerase in identifying damaged code sections during the transcription process. RNA polymerase then acts as a platform for the assembly of a DNA repair machine called nucleotide excision repair (NER) complex, which removes faulty DNA and replaces it with an accurate copy.

According to the team, the study provides the first evidence that ribonucleotide excision repair (RER) is tightly coupled to transcription, indicating a close cooperation between the key enzyme involved in RER, RNaseHII, and RNA polymerase in scanning for misincorporated ribonucleotides. These findings challenge existing notions in the DNA repair field and prompt a reevaluation of fundamental principles. The researchers plan to explore whether RNA polymerase scans DNA for various problems and triggers repair genome-wide in both bacterial and human cells.

The study employed cutting-edge techniques such as quantitative mass spectrometry, in vivo protein-protein crosslinking, and cryogenic electron microscopy (CryoEM) to determine the interactions and structures of RNaseHII and RNA polymerase. By mapping the distances between chemically linked proteins, the researchers identified the key surfaces involved in their interaction. CryoEM revealed high-resolution structures of RNaseHII bound to RNA polymerase, shedding light on the protein-protein interactions that define the RER complex. Genetic experiments weakening the RNA polymerase/RNaseHII interaction compromised the effectiveness of RER.

Ribonucleotide misincorporation is a common error during DNA replication, with DNA polymerase III making approximately 2,000 mistakes each time it copies a cell's genetic material. The RER pathway plays a crucial role in removing most misplaced ribonucleotides. The study's findings provide insights into how RNaseHII efficiently identifies rare ribonucleotide lesions amid a large quantity of intact DNA codes. The research contributes to the understanding of the DNA repair process and carries implications for clinical applications.