DNA Replication Checkpoint Activates Respiration in Budding Yeast

Abstract

In addition to DNA damage checkpoint (DDC), eukaryotic cells have also DNA replication checkpoint (DRC) that is distinct from the DDC and specifically signals slowly progressing or arrested replication forks. We have showed previously that DDC activates respiration to increase ATP production and to elevate dNTP levels, which are required for efficient DNA repair and cell survival upon DNA damage. The underlying mechanism involves DNA damage‐induced downregulation of histone expression and altered chromatin structure, leading to increased transcription of genes encoding enzymes of tricarboxylic acid cycle, electron transport chain (ETC), and oxidative phosphorylation. Here we show that similarly to DDC, activation of DRC also induces respiration. However, unlike DDC, DRC does not affect histone gene expression and chromatin structure. DRC induces respiration by inducing transcription of RNR1‐4, upregulating synthesis of dNTPs, and elevating mtDNA copy number. Fitness of rrm3∆ and sgs1∆, mutants with defects in DNA replication, requires checkpoint kinase Dun1, but does not require ETC and oxidative metabolism. However, in the absence of Dun1, ETC is required for viability of rrm3Δ and sgs1Δ cells. In addition, inactivation of ETC in dun1Δ cells results in a synthetic growth defect. Together, our data show that when Dun1p function is compromised, rrm3Δand sgs1Δ cells depend on oxidative metabolism.