Nova descoberta desafia princípio central em biologia: as células humanas podem escrever sequências de RNA no DNA

quarta-feira, junho 23, 2021

Polθ reverse transcribes RNA and promotes RNA-templated DNA repair

Gurushankar Chandramouly1,†, Jiemin Zhao2,†, Shane McDevitt1,†, Timur Rusanov1, Trung Hoang1, Nikita Borisonnik1, Taylor Treddinick1, Felicia Wednesday Lopezcolorado3, Tatiana Kent1, Labiba A. Siddique1, Joseph Mallon1, Jacklyn Huhn1, Zainab Shoda1, Ekaterina Kashkina1, Alessandra Brambati4, Jeremy M. Stark3, Xiaojiang S. Chen2 and Richard T. Pomerantz1,*

1 Department of Biochemistry and Molecular Biology, Sidney Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA, USA.

2 Molecular and Computational Biology, USC Dornsife Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA.

3 Beckman Research Institute of the City of Hope, Duarte, CA, USA.

4 Department of Cell Biology, New York University School of Medicine, New York, NY, USA.

↵*Corresponding author. Email:

↵† These authors contributed equally to this work.

Science Advances 11 Jun 2021: Vol. 7, no. 24, eabf1771


Genome-embedded ribonucleotides arrest replicative DNA polymerases (Pols) and cause DNA breaks. Whether mammalian DNA repair Pols efficiently use template ribonucleotides and promote RNA-templated DNA repair synthesis remains unknown. We find that human Polθ reverse transcribes RNA, similar to retroviral reverse transcriptases (RTs). Polθ exhibits a significantly higher velocity and fidelity of deoxyribonucleotide incorporation on RNA versus DNA. The 3.2-Å crystal structure of Polθ on a DNA/RNA primer-template with bound deoxyribonucleotide reveals that the enzyme undergoes a major structural transformation within the thumb subdomain to accommodate A-form DNA/RNA and forms multiple hydrogen bonds with template ribose 2′-hydroxyl groups like retroviral RTs. Last, we find that Polθ promotes RNA-templated DNA repair in mammalian cells. These findings suggest that Polθ was selected to accommodate template ribonucleotides during DNA repair.

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