Proteasome inhibitor differentially regulates expression of the major immediate early genes of human cytomegalovirus in human central nervous system-derived cell lines

• Published in: Virus research 2009-06, Vol.142 (1), p.68-77
• Main Authors: Sadanari, Hidetaka, Tanaka, Junji, Li, Zhuan, Yamada, Rie, Matsubara, Keiko, Murayama, Tsugiya
• Format: Article
• Language: English
• Subjects: Activating Transcription Factor 2 - genetics; Activating Transcription Factor 2 - metabolism; ATF-2; c-Jun; Cell Line; Central Nervous System - metabolism; Central Nervous System - virology; CRE; Cytomegalovirus; Cytomegalovirus - drug effects; Cytomegalovirus - genetics; Cytomegalovirus - metabolism; Cytomegalovirus Infections - genetics; Cytomegalovirus Infections - metabolism; Cytomegalovirus Infections - virology; Gene Expression Regulation, Viral - drug effects; Human cytomegalovirus; Humans; Immediate-Early Proteins - genetics; Immediate-Early Proteins - metabolism; Lactones - pharmacology; Leupeptins - pharmacology; Major immediate-early gene; MIE promoter/enhancer; Neuroblastoma; NF-κB; Oligopeptides - pharmacology; Protease Inhibitors - pharmacology; Proteasome inhibitor; Proteasome Inhibitors; Proto-Oncogene Proteins c-jun - genetics; Proto-Oncogene Proteins c-jun - metabolism
• ISSN: 0168-1702; 1872-7492
• DOI: 10.1016/j.virusres.2009.01.010

Proteasome inhibitor, which inhibits NF-κB activation, has been reported to activate c-Jun N-terminal kinase (JNK)-c-Jun pathway. In this study, we investigated the effects of proteasome inhibitor on the human cytomegalovirus (HCMV) major immediate early (MIE) gene expression in human central nervous system (CNS)-derived cell lines. Treatment of HCMV-infected 118MGC glioma and U373-MG astrocytoma cells with three proteasome inhibitors, MG132, clasto-lactacystin β-lactone, and epoxomicin, suppressed MIE protein expression. In contrast, in HCMV-infected IMR-32 neuroblastoma cells, the proteasome inhibitors increased MIE protein expression, even in the presence of NF-κB inhibitor SN-50. A luciferase reporter assay demonstrated that MG132 markedly elevated the MIE promoter/enhancer (MIEP) activity in IMR-32 cells, but down-regulated it in 118MGC and U373-MG cells. Mutation in five cAMP response elements (CREs) within the MIEP resulted in a loss of the ability to respond to MG132 in IMR-32 cells. Moreover, Western blotting analysis revealed that MG132 induced c-Jun phosphorylation in all three CNS-derived cell lines, whereas a high level of activating transcription factor-2 (ATF-2) phosphorylation was observed only in IMR-32 cells. Finally, MG132-induced MIE protein expression was suppressed by JNK inhibitor that reduced the phosphorylation levels of both c-Jun and ATF-2. Taken together, these results suggest that the proteasome inhibitors activate CRE binding proteins consisting of c-Jun and ATF-2 through activating the JNK-c-Jun pathway, thereby inducing MIE protein synthesis in IMR-32 cells under the condition where NF-κB activity is inhibited.