ATR kinase supports normal proliferation in the early S phase by preventing replication resource exhaustion

The ATR kinase, which coordinates cellular responses to DNA replication stress, is also essential for the proliferation of normal unstressed cells. Although its role in the replication stress response is well defined, the mechanisms by which ATR supports normal cell proliferation remain elusive. Here, we show that ATR is dispensable for the viability of G0-arrested naive B cells. However, upon cytokine-induced proliferation, Atr-deficient B cells initiate DNA replication efficiently, but by mid-S phase they display dNTP depletion, fork stalling, and replication failure. Nonetheless, productive DNA replication and dNTP levels can be restored in Atr-deficient cells by suppressing origin firing, such as partial inhibition of CDC7 and CDK1 kinase activities. Together, these findings indicate that ATR supports the proliferation of normal unstressed cells by tempering the pace of origin firing during the early S phase to avoid exhaustion of dNTPs and importantly also other replication factors. The ATR kinase has essential functions apart from its role in DNA replication stress. Here the authors find that in mouse primary B cells ATR tempers the pace of origin firing during the early S phase to avoid exhaustion of dNTPs and other replication factors.

Automated summary

The ATR kinase is crucial for the replication stress response and also supports normal cell proliferation by regulating origin firing to prevent depletion of dNTPs and other replication factors.