The Chromatin Remodeling Factor SMARCB1 Forms a Complex with Human Cytomegalovirus Proteins UL114 and UL44 Toril Ranneberg-Nilsen1,3, Halvor Rollag1, Ragnhild Slettebakk1, Paul Hoff Backe1,2,3, Øyvind Olsen1,2,3, Luisa Luna1,3, Magnar Bjøra˚ s1,2,3* 1 Department of Microbiology, University of Oslo and Oslo University Hospital HF, Rikshospitalet, Oslo, Norway, 2 Department of Medical Biochemistry, University of Oslo and Oslo University Hospital HF, Rikshospitalet, Oslo, Norway, 3 Centre for Molecular Biology and Neuroscience, University of Oslo and Oslo University Hospital HF, Rikshospitalet, Oslo, Norway Abstract Background: Human cytomegalovirus (HCMV) uracil DNA glycosylase, UL114, is required for efficient viral DNA replication. Presumably, UL114 functions as a structural partner to other factors of the DNA-replication machinery and not as a DNA repair protein. UL114 binds UL44 (HCMV processivity factor) and UL54 (HCMV-DNA-polymerase). In the present study we have searched for cellular partners of UL114. Methodology/Principal Findings: In a yeast two-hybrid screen SMARCB1, a factor of the SWI/SNF chromatin remodeling complex, was found to be an interacting partner of UL114. This interaction was confirmed in vitro by co- immunoprecipitation and pull-down. Immunofluorescence microscopy revealed that SMARCB1 along with BRG-1, BAF170 and BAF155, which are the core SWI/SNF components required for efficient chromatin remodeling, were present in virus replication foci 24–48 hours post infection (hpi). Furthermore a direct interaction was also demonstrated for SMARCB1 and UL44. Conclusions/Significance: The core SWI/SNF factors required for efficient chromatin remodeling are present in the HCMV replication foci throughout infection. The proteins UL44 and UL114 interact with SMARCB1 and may participate in the recruitment of the SWI/SNF complex to the chromatinized virus DNA. Thus, the presence of the SWI/SNF chromatin remodeling complex in replication foci and its association with UL114 and with UL44 might imply its involvement in different DNA transactions. Citation: Ranneberg-Nilsen T, Rollag H, Slettebakk R, Backe PH, Olsen Ø, et al. (2012) The Chromatin Remodeling Factor SMARCB1 Forms a Complex with Human Cytomegalovirus Proteins UL114 and UL44. PLoS ONE 7(3): e34119. doi:10.1371/journal.pone.0034119 Editor: Alison J. Sinclair, University of Sussex, United Kingdom Received September 7, 2011; Accepted February 22, 2012; Published March 27, 2012 Copyright: 2012 Ranneberg-Nilsen et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The work was supported by Norwegian Research Council and Health South-East, Norway. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: magnar.bjoras@rr-research.no Introduction The human cytomegalovirus (HCMV), a member of the Betaherpesviridae, is an important human pathogen. It is the major viral cause of birth defects [1,2] and represents a major medical problem in immunocompromised individuals, such as AIDS patients and patients with allogenic solid organ or stem cells transplants [3–5]. The HCMV-genome is one of the largest human DNA-virus genomes (230 kbp) with about 200 predicted open reading frames [6]. After binding of HCMV to cell surface receptors the virus membrane and cell membrane fuse, and the nucleocapsid is released into the cytoplasm. The nucleocapsid transverses the cytoplasm by association with the microtubules network and gain access to the nuclear pores where the uncoating is completed and the viral genome is released into the nucleoplasm [7]. Immediately after entering the nucleoplasm the viral DNA is circularized, histone proteins bind to virus DNA and nucleosomes are formed [8,9]. The HCMV genomes serve as templates for transcription and replication, thought to take place within discrete nuclear inclusions. These inclusions develop adjacent to small sites known as promyelocytic leukemia bodies or nuclear domain 10 and take over large parts of the nuclear space at late times post infection [10,11]. HCMV replication requires a conserved set of six core DNA replication proteins: the DNA polymerase (UL54) and the associated polymerase processivity factor (UL44), a single-stranded DNA binding protein (SSB; UL57), and the triplex containing DNA helicase (UL105), primase (UL70) and primase-associated factor (UL102) subunits [6,12,13]. HCMV UL114 encodes a uracil-DNA glycosylase homolog that is highly conserved in all characterized herpesviruses that infect mammals [14]. Analysis of HCMV-DNA replication kinetics performed using a HCMV UL114 deletion mutant has shown that the initial rate of DNA synthesis and the accumulation of progeny viral genomes were significantly reduced compared to the parent virus [15,16]. UL114 is thus obviously of importance for several steps in HCMV-DNA synthesis. PLoS ONE | www.plosone.org 1 March 2012 | Volume 7 | Issue 3 | e34119