Evidence from several studies indicates that the DNA genome of herpesviruses is devoid of any nucleosomes within the virus particle 
. In contrast, in infected nuclei, herpesvirus genomes form structures that resemble cellular chromatin and these structures change in composition throughout the time course of infection 
. As early as two hours post infection, a fraction of the HCMV genomes is associated with histones, but eventually, the HCMV progeny genomes have to be stripped naked before being packaged 
. Factors involved in DNA replication, repair and transcription do not get access to DNA packed in chromatin and thus have to act in concert with chromatin modifiers and remodelers that loosen the chromatin grip on DNA. The SWI/SNF family of chromatin remodeling complex utilizes the energy of ATP hydrolysis to remodel chromatin structures, thereby participating in gene regulation, replication, viral integration, control of cell growth and tumor suppression 
. SMARCB1 was initially identified as a cellular partner to the HIV-1 integrase 
. Subsequent studies have revealed the interaction of SMARCB1 or other subunits of the SWI/SNF complex with viral proteins from human papillomavirus 
, Epstein-Barr virus 
, Kaposi's sarcoma-associated herpes virus 
and herpes simplex virus −1 
. Collectively, these studies have shown that the SWI/SNF complex is crucial for effective viral gene transcription and DNA replication. In search for cellular partners of UL114, a nearly full-length SMARCB1 clone was identified as an interacting partner. The direct interaction between UL114 and SMARCB1 was validated in vitro
by three different experiments.
UL114 has been found to interact with UL44 and this complex was highly enriched in viral replication foci 
. Since co-localization between UL114 and SMARCB1 could not be carried out, UL44 was used as a replication marker. By this mean we showed that SMARCB1 co-localizes to replication foci as early as 24 hpi. The SWI/SNF complex consists of at least nine subunits that are conserved among eukaryotes 
. Four of the subunits; the central ATPase subunit, either hBRM (Bramha) or Bramha-related gene-1 (BRG-1), SMARCB1, BAF170 and BAF155 are required for efficient chromatin remodeling 
. Our results demonstrate that the expression of these core subunits of the SWI/SNF chromatin remodeling complex increased during HCMV infection and were relocated to and concentrated in virus replication foci of HCMV-infected fibroblasts. To our knowledge, this is the first time a chromatin remodeling complex has been detected in virus replication foci in HCMV. Furthermore, interaction between SMARCB1 and UL44 was demonstrated both by detection of SMARCB1 in cell extracts precipitated with anti-UL44 antibodies and by direct interaction between recombinant proteins. Thus, we have evidence of direct interactions between SMARCB1 and UL114 and SMARCB1 and UL44. The UL44 and/or UL114 proteins may be of importance to recruit and stabilize the SWI/SNF chromatin remodeling complex to the replication centers.
The human HCMV DNA polymerase is composed of a catalytic subunit, UL54, which possesses basal DNA polymerase activity 
, and the accessory protein, UL44 which has been shown to specifically interact with UL54 and to stimulate long-chain DNA synthesis by UL54 
. UL44 is a multifunctional protein capable of associating/interacting with several other viral and host proteins 
. Viral replication centers also serve as foci for viral gene expression, presumably in part by concentrating templates for transcription with the proteins that carry out or regulate this process. Thus, the presence of the SWI/SNF chromatin remodeling complex in replication foci throughout infection and its association with UL114 and with UL44 might imply its involvement in different DNA transactions. For example, it has been shown that the UL44 gene product from the late viral transcript is required for efficient viral gene expression rather than viral DNA synthesis 
. Comparable to the herpes simplex virus type-1 single-strand DNA-binding protein, ICP8, which co-precipitates with chromatin remodeling factors 
, UL44 could recruit the SWI/SNF complex to late viral promoters at late times after infection.
Finally, although controversial and ill-defined, the nuclear matrix, also referred to as nucleoskeleton or scaffold, organizes the eukaryotic DNA into topologically distinct loops. This is generated by the attachment of chromatin fibers to the nuclear matrix via specific regions called scaffold or matrix attachment regions S/MAR 
. DNA replication and transcription of active DNA are found tightly associated with the nuclear matrix, while inactive loci are not 
. Several studies have reported replication and expression of viral genomes in association with the nuclear matrix 
. SMARCB1 has been found to be associated with the nuclear matrix and chromatin 
. UL44 has also been shown to be associated with the nuclear matrix 
. By fractionating the nucleus into the sub-nuclear structures; chromatin and nuclear matrix, we showed that in addition to SMARCB1 and UL44, UL114 was present in the chromatin and nuclear matrix fraction, but highly enriched in the chromatin fraction. However, it remains to be investigated whether SMARCB1, UL114 and UL44 associate in one complex and/or as different complexes (in the nuclear matrix and/or associated with chromatin) throughout the time course of infection allowing chromatin remodeling both during DNA replication, DNA transcription and DNA packaging.