ATR and ATM play both distinct and additive roles in response to ionizing radiation

TLDR

ATR and ATM protein kinases are involved in diverse DNA‑damage responses, and Arabidopsis thaliana contains both orthologs whose null mutants remain viable. The study performed a short‑term global transcription analysis of wild‑type and mutant Arabidopsis lines to characterize the roles of ATM and ATR in ionizing‑radiation response. Mutants lacking ATR or ATM are hypersensitive to γ‑irradiation; transcriptomic analysis showed that ATM, but not ATR, drives the induction of hundreds of genes, including the cyclin CYCB1;1, whose expression is rapidly upregulated by IR and requires both kinases for induction but only ATR for sustained expression, suggesting a novel DNA‑damage role for CYCB1;1 rather than G2 arrest.

Abstract

Summary The ATR and ATM protein kinases are known to be involved in a wide variety of responses to DNA damage. The Arabidopsis thaliana genome includes both ATR and ATM orthologs, and plants with null alleles of these genes are viable. Arabidopsis atr and atm mutants display hypersensitivity to γ ‐irradiation. To further characterize the roles of ATM and ATR in response to ionizing radiation, we performed a short‐term global transcription analysis in wild‐type and mutant lines. We found that hundreds of genes are upregulated in response to γ ‐irradiation, and that the induction of virtually all of these genes is dependent on ATM , but not ATR . The transcript of C YCB1;1 is unique among the cyclin transcripts in being rapidly and powerfully upregulated in response to ionizing radiation, while other G 2 ‐associated transcripts are suppressed. We found that both ATM and ATR contribute to the induction of a CYCB1;1:GUS fusion by IR, but only ATR is required for the persistence of this response. We propose that this upregulation of CYCB1;1 does not reflect the accumulation of cells in G 2 , but instead reflects a still unknown role for this cyclin in DNA damage response.