Topoisomerase I-driven repair of UV-induced damage in NER-deficient cells.

Abstract

Nucleotide excision repair (NER) removes helix-destabilizing adducts including ultraviolet (UV) lesions, cyclobutane pyrimidine dimers (CPDs), and pyrimidine (6-4) pyrimidone photoproducts (6-4PPs). In comparison with CPDs, 6-4PPs have greater cytotoxicity and more strongly destabilizing properties of the DNA helix. It is generally believed that NER is the only DNA repair pathway that removes the UV lesions as evidenced by the previous data since no repair of UV lesions was detected in NER-deficient skin fibroblasts. Topoisomerase I (TOP1) constantly creates transient single-strand breaks (SSBs) releasing the torsional stress in genomic duplex DNA. Stalled TOP1-SSB complexes can form near DNA lesions including abasic sites and ribonucleotides embedded in chromosomal DNA. Here we show that base excision repair (BER) increases cellular tolerance to UV independently of NER in cancer cells. UV lesions irreversibly trap stable TOP1-SSB complexes near the UV damage in NER-deficient cells, and the resulting SSBs activate BER. Biochemical experiments show that 6-4PPs efficiently induce stable TOP1-SSB complexes, and the long-patch repair synthesis of BER removes 6-4PPs downstream of the SSB. Furthermore, NER-deficient cancer cell lines remove 6-4PPs within 24 h, but not CPDs, and the removal correlates with TOP1 expression. NER-deficient skin fibroblasts weakly express TOP1 and show no detectable repair of 6-4PPs. Remarkably, the ectopic expression of TOP1 in these fibroblasts led them to completely repair 6-4PPs within 24 h. In conclusion, we reveal a DNA repair pathway initiated by TOP1, which significantly contributes to cellular tolerance to UV-induced lesions particularly in malignant cancer cells overexpressing TOP1.

• Authors: Liton Kumar Saha, Mitsuo Wakasugi, Salma Akter, Rajendra Prasad, Samuel H Wilson, Naoto Shimizu, Hiroyuki Sasanuma, Shar-Yin Naomi Huang, Keli Agama, Yves Pommier, Tsukasa Matsunaga, Kouji Hirota, Shigenori Iwai, Yuka Nakazawa, Tomoo Ogi, Shunichi Takeda
• Journal: Proceedings of the National Academy of Sciences of the United States of America (Proc Natl Acad Sci U S A) Vol. 117 Issue 25 Pg. 14412-14420 (06 23 2020) ISSN: 1091-6490 [Electronic] United States
• PMID: 32513688 (Publication Type: Journal Article, Research Support, N.I.H., Intramural, Research Support, Non-U.S. Gov't)

Chemical References

• X-ray Repair Cross Complementing Protein 1
• XPA protein, human
• XRCC1 protein, human
• Xeroderma Pigmentosum Group A Protein
• DNA Polymerase beta
• POLB protein, human
• DNA Topoisomerases, Type I
• TOP1 protein, human

Topics

• CRISPR-Cas Systems (genetics)
• DNA Breaks, Single-Stranded (radiation effects)
• DNA Polymerase beta (genetics, metabolism)
• DNA Repair
• DNA Topoisomerases, Type I (metabolism)
• Fibroblasts
• Gene Knockout Techniques
• Humans
• MCF-7 Cells
• Primary Cell Culture
• Skin (cytology, pathology, radiation effects)
• Ultraviolet Rays (adverse effects)
• X-ray Repair Cross Complementing Protein 1 (genetics, metabolism)
• Xeroderma Pigmentosum (etiology, pathology)
• Xeroderma Pigmentosum Group A Protein (genetics, metabolism)