HMGB1-specific antibody was purchased from Cell Signal (catalog number 3935S). viral DNA in latent and lytic models. Given the strong association of cellular factors with herpesvirus lytic origins of replication we investigated if HCMV oriLyt interacts with cellular factors. In the present study we identified several viral- and cellular-encoded factors that bind to immobilized oriLyt bait DNA. We followed essentially the same protocol used for identification of cellular/viral factors that contribute to KSHV oriLyt and terminal repeat regions (Si et al., 2006; Verma et al., 2006; Wang et al., 2008). Using this approach, we were able to confirm the presence of Teglicar several viral factors known to interact with oriLyt, as well as identify both viral and cellular factors previously unknown to bind to oriLyt DNA. The HCMV replication proteins UL84, UL44, and IE2 were confirmed to bind to oriLyt. In addition, we also identified interactions between IRS1 and UL112/113 proteins with oriLyt. Some cellular-encoded proteins, including the mitotic checkpoint protein BUB3, polypryrimidine tract protein (PTB)Cassociated splicing factor, and heterogeneous ribonuclear protein K (hnRNP K) were also found to bind to immobilized oriLyt DNA, suggesting a possible role Teglicar in HCMV DNA replication. Since hnRNP K was shown to have a central role in other herpesviruses we in investigated further the role of this protein in HCMV lytic DNA replication. We show that hnRNP K interacts with the HCMV UL84 and inhibition of hnRNP K by siRNA knockdown severely reduces oriLyt amplification Rabbit polyclonal to RABAC1 in the transient cotransfection replication assay. Together, these results signify a role for these cellular factors in the regulation of viral DNA replication and virus growth. RESULTS Identification of proteins that interact with HCMV oriLyt To identify proteins that interact with HCMV oriLyt, we used a DNA-affinity column to capture proteins isolated from HCMV-infected nuclei. pGEM plasmid containing the oriLyt sequence coupled to a cyanogen bromide-activated sepharose column was incubated with infected-cell nuclear extract, washed, and bound material eluted with 150 mM, 500 mM, and 1M NaCl. Bound protein was resolved on an 8C12% polyacrylamide gel and stained with Coomassie Blue (Fig. 1A). In order to ensure specific binding to oriLyt sequences and to eliminate proteins that non-specifically interact with DNA, we used a column coupled with pGEM vector DNA. Proteins within nuclear extracts were bound to each column and subsequently eluted from both columns. Proteins present in the salt elutions were separated by 2D-gel electrophoresis. A paired set of representative 2-D gels is shown (Fig. 1B). 2-D gels were analyzed and protein spots Teglicar not present in the pGEM control sample were isolated, digested with trypsin, and the peptides subjected to MS/MS for identification. Proteins that were identified by this approach are listed in Table 1. Open in a separate window Figure 1 Identification of viral and cellular factors that bind to HCMV oriLyt(A) Increasing salt elutions of affinity-purified protein bound to oriLyt DNA immobilized on a CNBr column. Eluates were separated on Teglicar a 4C12% bis-Tris NuPage gel and stained with Coomassie blue. (B) Representative 2-D PAGE gels of eluted protein from 500mM NaCl elutions for oriLyt (left panel) or pGEM (right Teglicar panel) affinity columns. Table 1 OriLyt binding proteins identified from affinity column chromatography. for 5 minutes, the supernatant removed, and resuspended in hypotonic lysis buffer plus protease inhibitors and 0.1M DTT. The suspension was incubated at room temperature for 15 minutes, centrifuged at 450 for 5 minutes, and the supernatant removed. Hypotonic lysis buffer with protease inhibitors and DTT was added, and the cells were dounce- homogenized (type B pestle) with seven strokes on ice. Homogenized samples were centrifuged at 10,000 rpm in a tabletop centrifuge for 10 minutes at 4C and the cytoplasmic fraction (supernatant) was transferred to a new tube. The pellet was resuspended in extraction buffer, homogenized with 10 strokes, and gently shaken for 30 minutes at 4C. Extracted nuclei were collected.
