An essential role for dNTP homeostasis following CDK-induced replication stress

Abstract

Replication stress is a common feature of cancer cells, and thus a potentially important therapeutic target. Here we show that CDK-induced replication stress is synthetic lethal with mutations disrupting dNTP homeostasis in fission yeast. Wee1 inactivation leads to increased dNTP demand and replication stress through CDK-induced firing of dormant replication origins. Subsequent dNTP depletion leads to inefficient DNA replication, Mus81-dependent DNA damage, and to genome instability. Cells respond to this replication stress by increasing dNTP supply through Set2-dependent MBF-induced expression of Cdc22, the catalytic subunit of ribonucleotide reductase (RNR). Disrupting dNTP synthesis following Wee1 inactivation, through abrogating Set2-dependent H3K36 tri-methylation or DNA integrity checkpoint inactivation results in critically low dNTP levels, replication collapse and cell death, which can be rescued by increasing dNTP levels. These findings support a dNTP supply and demand model in which maintaining dNTP homeostasis is essential to prevent replication catastrophe in response to CDK-induced replication stress.