We previously presented that calmodulin-dependent kinase IV (CaMKIV) mutually interacts with NF-kappaB and phosphorylates it directly, inducing the increased transcriptional regulation dependent on NF-kappaB target genes [J. Biol. Chem. 276 (2001) 20005]. Here, we show that Ser(535) residue is phosphorylated by CaMKIV. S535A mutant of p65 was specifically defective in transactivation of NF-kappaB target gene expression induced by CaMKIV. While coexpression of active CaMKIV with wild-type p65 led to a recovery from etoposide-induced apoptosis and an increase of Bcl-2 protein in cells, cells expressing S535A mutant did not. Taken together these results suggest that phosphorylated NF-kappaB p65 on Ser(535) by CaMKIV increases NF-kappaB target gene expression, including antiapoptotic gene, hence leading to inhibition of apoptosis. (C) 2003 Elsevier Science (USA). All rights reserved.