Functional interaction of protein kinase CK2 and activating transcription factor 4 (ATF4), a key player in the cellular stress response

► ATF4 is a new binding partner of protein kinase CK2. ► CK2 phosphorylates ATF4 at serine 215. ► Phosphorylation of ATF4 by CK2 reduces the stability of ATF4. ► Inhibition of CK2 kinase activity results in an elevated transcription of ATF4. ► CK2 phosphorylation of ATF4 stimulates its transcription factor activity.