Control of human cytomegalovirus gene expression by differential histone modifications during lytic and latent infection of a monocytic cell line ✩ Elena Ioudinkova a,b,1 , Maria Cristina Arcangeletti a, ⁎ ,1 , Alla Rynditch a,c , Flora De Conto a , Federica Motta a , Silvia Covan a , Federica Pinardi a , Sergey V. Razin a,b , Carlo Chezzi a a Microbiology Section, Department of Pathology and Laboratory Medicine, University of Parma, Viale Antonio Gramsci, 14, 43100 Parma, Italy b Institute of Gene Biology, Russian Academy of Science, Moscow, Russia c Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, Kiev, Ukraine Received 23 May 2006; received in revised form 23 June 2006; accepted 4 July 2006 Available online 31 July 2006 Abstract Non-differentiated THP-1 cells can be infected by human cytomegalovirus (HCMV) Towne strain, which persists in these cells in a non-active (latent) form without undergoing a productive cycle. The same cells become permissive for HCMV lytic infection after induction of cell differentiation by treatment with 12-O-tetradecanoylphorbol-13-acetate. We used this cellular model to study the possible role of histone modifications in the control of HCMV latency. Using chromatin immunoprecipitation with antibodies against histone H3 acetylated or dimethylated in position K9, we demonstrated that in lytically infected cells the HCMV enhancer was associated with heavy acetylated but not dimethylated H3. In the case of latent infection, the HCMV enhancer was associated with neither acetylated nor dimethylated H3. HCMV genes encoding DNA polymerase (early), pp65 (early–late) and pp150 (late) proteins were associated preferentially with acetylated H3 in lytically infected cells and with dimethylated H3 in latently infected cells. These data strongly suggest that K9 methylation of H3 is involved in HCMV gene repression, while association of the above genes with acetylated histones is likely to be necessary for active transcription. It can be postulated that the same histone modifications are used to mark active and repressed genes in both cellular and viral chromatin. © 2006 Elsevier B.V. All rights reserved. Keywords: Cytomegalovirus latency; Gene repression; Histone methylation; THP-1 monocytic cell line 1. Introduction Human cytomegalovirus (HCMV) is a ubiquitous human pathogen. Although infection with this virus is asymptomatic in otherwise healthy individuals, it may cause serious diseases particularly in immunocompromised persons (Escuissato et al., 2005; Griffiths and Walter, 2005; Magro et al., 2005; Rowshani et al., 2005; Schleiss and McVoy, 2004). This happens when HCMV, persisting lifelong in a latent condition in normal indi- viduals, switches to a productive cycle. The mechanisms which make some cells permissive for lytic infection and others non- permissive are largely unknown. In infected cells (irrespective of the type of infection), the viral DNA is packed into nucleosomes and, perhaps, in higher order chromatin structures (Chen et al., 1997; Murphy et al., 2002; Reeves et al., 2005; St Jeor et al., 1982). Recent studies have demonstrated that histone modifications play a crucial role in the regulation of cellular gene transcription and also in facilitating the transcription of templates packed in nucleosomes (“transcription through nucleosomes”)(Imhof, 2003; Khan and Krishnamurthy, 2005; Margueron et al., 2005; Vermaak et al., 2003). Furthermore, it becomes increasingly Gene 384 (2006) 120 – 128 www.elsevier.com/locate/gene Abbreviations: aa, amino acid(s); Ab, antibody(ies); bp, base pair(s); BSA, bovine serum albumin; cDNA, DNA complementary to RNA; DNase, deoxyribonuclease; dNTPs, deoxyribonucleoside triphosphate; DTT, dithio- threitol; EtdBr, ethidium bromide; FBS, foetal bovine serum; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; HCMV, human cytomegalovirus; Hepes, 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid; IE, Immediate– Early; kb, kilobase(s); kDa, kilodalton(s); mAb, monoclonal Ab; moi, multiplicity of infection; pfu, plaque forming unit(s); Pipes, 1,4-piperazinediethanesulfonic acid; PMSF, phenylmethylsulfonyl fluoride; SDS, sodium dodecyl sulfate; Sm, streptomycin; TPA, 12-O-tetradecanoylphorbol-13-acetate; U, unit(s). ✩ This article is dedicated to the memory of Christophe Mérieux. ⁎ Corresponding author. Tel.: +39 0521988877; fax: +39 0521993620. E-mail address: mariacristina.arcangeletti@unipr.it (M.C. Arcangeletti). 1 Elena Ioudinkova and Maria Cristina Arcangeletti contributed equally to this paper. 0378-1119/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.gene.2006.07.021