Bypassing a 8,5′-cyclo-2′-deoxyadenosine lesion by human DNA polymerase η at atomic resolution

• Published in: Proceedings of the National Academy of Sciences - PNAS 2018-10, Vol.115 (42), p.10660-10665
• Main Authors: Weng, Peter J., Gao, Yang, Gregory, Mark T., Wang, Pengcheng, Wang, Yinsheng, Yang, Wei
• Format: Article
• Language: English
• Subjects: Adenine; Adenosine; Atoms & subatomic particles; Base Pairing; Biological Sciences; Calcium - chemistry; Calcium - metabolism; Crystal structure; Crystallography, X-Ray; Cytotoxicity; Deoxyadenosine; Deoxyadenosines - toxicity; Deoxyribonucleic acid; Dimers; DNA; DNA biosynthesis; DNA Damage; DNA polymerase; DNA Repair; DNA Replication; DNA-directed DNA polymerase; DNA-Directed DNA Polymerase - chemistry; DNA-Directed DNA Polymerase - metabolism; Humans; Lesions; Magnesium - chemistry; Magnesium - metabolism; Manganese - chemistry; Manganese - metabolism; Models, Molecular; Molecular structure; Mutagens; Nucleotide excision repair; Nucleotides - chemistry; Nucleotides - metabolism; Protein Conformation; Proteins; Repair; Replication; Thymine; Transcription
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1812856115

Oxidatively induced DNA lesions 8,5′-cyclopurine-2′-deoxynucleosides (cdPus) are prevalent and cytotoxic by impeding DNA replication and transcription. Both the 5′R- and 5′S-diastereomers of cdPu can be removed by nucleotide excision repair; however, the 5′S-cdPu is more resistant to repair than the 5′R counterpart. Here, we report the crystal structures of human polymerase (Pol) η bypassing 5′S-8,5′-cyclo-2′-deoxyadenosine (cdA) in insertion and the following two extension steps. The cdA-containing DNA structures vary in response to the protein environment. Supported by the “molecular splint” of Pol η, the structure of 5′S-cdA at 1.75-Å resolution reveals that the backbone is pinched toward the minor groove and the adenine base is tilted. In the templating position, the cdA takes up the extra space usually reserved for the thymine dimer, and dTTP is efficiently incorporated by Pol η in the presence of Mn2+. Rigid distortions of the DNA duplex by cdA, however, prevent normal base pairing and hinder immediate primer extension by Pol η. Our results provide structural insights into the strong replication blockage effect and the mutagenic property of the cdPu lesions in cells.