In response to environmental stresses, cells activate stress-response genes and inhibit DNA replication. HBO1 histone acetylase is a coactivator both for AP-1 transcription factors responding to stress-activated JNK kinases and also for the Cdt1 licensing factor that ensures that DNA is replicated exactly once per cell cycle. In response to non-genotoxic stress, JNK phosphorylates Jun, an AP-1 transcription factor, leading to increased recruitment of HBO1 and increased transcription of target genes. In addition, JNK phosphorylates Cdt1 on threonine 29, leading to rapid dissociation of HBO1 from replication origins, thereby blocking initiation of DNA replication. Upon relief of stress, HBO1 re-associates with replication origins. Thus, regulated and reciprocal recruitment of the HBO1 co-activator to target genes and replication origins via JNK-mediated phosphorylation of the recruiting transcription and replication licensing factors coordinates the transcriptional and DNA replication response to cellular stress.