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bioRxiv · 10.1101/2022.03.10.483800

ATR-I774Yfs*5 promotes genomic instability through micronuclei formation

D'Orazio, J.·Holcomb, N.·Pu, H.·Dhar, B.·Bautista, R.·Overmann, A.·Shelton, B.·Corum, L.
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Abstract

Although mismatch repair (MMR) defects are associated with high risk of malignancy, the specific oncogenic drivers pertinent to MMR-affected cancers are poorly characterized. The heterozygous ATR-I774Yfs*5 mutation, the result of strand slippage in a poly-A tract of the Ataxia Telangiectasia and Rad3 related (ATR) gene, is overexpressed in MMR-defective malignancies including colorectal carcinoma (CRC) and is the most common ATR mutation in cancer. Here, we explore the contribution of ATR-I774Yfs*5 to genomic integrity. Using heterozygous ATR-I774Yfs*5 HCT-116 cells to mimic the native mutation, we found this mutation reduced ATR activity as measured by damage-induced Chk1 phosphorylation at S317 and ATR autophosphorylation ATR at T1989. ATR-I774Yfs*5 expression impaired genomic stability as visualized by the appearance of micronuclei in two stable expression models as well as in cell lines transfected with ATR-I774Yfs*5. Micronucleus development was dependent on replication and independent of ATR copy number. ATR-I774Yfs*5 expression did not alter cellular viability, cell cycle progression, or replicative rate, suggesting this mutation is well-tolerated despite its destabilizing effect on the genome. Taken together, these data suggest that the ATR-I774Yfs*5, whose development is favored in the context of MMR deficiency, may represent an important driver of a mutator phenotype by promoting genomic instability.

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D'Orazio, J., Holcomb, N., Pu, H., Dhar, B., Bautista, R., Overmann, A., Shelton, B., Corum, L.. 2022-03-12. ATR-I774Yfs*5 promotes genomic instability through micronuclei formation. https://doi.org/10.1101/2022.03.10.483800

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