The 171-amino acid sequence of vBcl-2 is indicated at the top with the α-helical structures numbered according to previous publication [25]. Colored boxes denote the BH 1–4 domains in vBcl-2. “+” : positive interaction, “−” : no interaction. L: linker region; TM: transmembrane domain; Triple arrows denote the alanine substitutions at Ser85-Gly86-Arg87 within the BH1 domain of vBcl-2.

(A) Co-immunoprecipitation (Co-IP) of Beclin1 with WT or mutant vBcl-2. 293T cells were transiently transfected with the indicated constructs, followed by immunoprecipitation of HA-tagged vBcl-2 and immunoblotting of V5-tagged Beclin1. (B) Co-IP of WT or mutant vBcl-2 with endogenous Beclin1. 293T cells were transfected with the indicated vBcl-2 constructs, followed by immunoprecipitation of HA-tagged vBcl-2 and immunoblotting of endogenous Beclin1. 1% whole-cell lysates (WCLs) was used as the input. (C) vBcl-2 interaction with Bak protein. 293T cells were transfected with WT and mutant forms of vBcl-2 as indicated. At 48 h posttransfection, WCLs were mixed either with GST-BakΔTM fusion protein (left panel) or with GST alone (right panel) for an in vitro GST pull-down (GST PD) assays. GST fusion proteins used for the pulldown assay are indicated (bottom panel). 1% WCL was used as the input. Data are representative of at least three experiments yielding similar results.

(A) NIH3T3 cells stably expressing the WT and mutant forms of vBcl-2 were transfected with GFP-LC3. At 18 h posttransfection, cells were incubated under normal or starvation conditions for 4 h. Autophagy was quantified as mean±SEM of the combined results from three independent experiments. **, P<0.0001. (B) NIH3T3 cells expressing the WT or mutant forms of vBcl-2 as indicated were transfected with GFP-LC3 and treated with 2 µM rapamycin for 6 h. GFP-LC3 was detected using an inverted fluorescence microscope (top). Autophagy was quantified as mean±SEM of the combined results from three independent experiments. Scale bar, 5 µm; **, P<0.01. (C) NIH3T3 cells stably expressing the WT or mutant forms of vBcl-2, as indicated, were treated with 2 µM rapamycin. LC3-I and LC3-II levels were then determined by immunoblotting with an antibody against LC3 (top). Densitometric quantification of the LC3-II/LC3-I ratios under normal and rapamycin treatment conditions is shown at the bottom. Similar results were obtained from three independent experiments.

(top) Representative confocal images of GFP-LC3 and HA-tagged vBcl-2 (WT and mutants) in NIH3T3 cells infected with the indicated viruses (MOI = 5). Nuclei were counterstained with 4′,6′-diamidino-2-phenylindole (DAPI). Scale bar, 5 µm. (bottom) Quantification of the percentage of virally infected cells with GFP-LC3 punctate staining. Results shown represent mean±SEM of combined results from three independent experiments (200 cells per experimental condition). *, P<0.01 versus HA-WT; **, P<0.001 versus HA-WT.

NIH3T3 cells stably expressing the WT or mutant forms of vBcl-2 were treated with TNFα and cycloheximide (CHX) for 12 h, then assayed for cell viability by trypan blue exclusion assay (A), or for apoptosis by TUNEL staining (B) or for the caspase 3 activation using flow cytometry (C). Apoptotic cells in (B) were counted under high power magnification (60×magnification). Mock, untreated condition. Data represents mean±SEM of combined results from three independent experiments. Scale bars, 100 µm (A), 5 µm (B). **, P<0.0001 versus vector cells.

(A) Single-step (right) and multiple-step (left) growth curves of the WT and recombinant γHV68 viruses in BHK21 cells. (B) Acute replication of the WT and mutant vBcl-2 γHV68 viruses in the lungs of BALB/c mice at 5 dpi (up) and 7 dpi (down) after intranasal infection determined by viral titers in the lungs of the infected mice (left) or by real-time PCR of the viral genomic DNA (right). Mean±SEM of five mice per group/experiment. Data of 7 dpi is pooled from two separate experiments. The vBcl-2 Δα1 and ΔBH2 mutants did not yield significantly different results when compared to the WT in infectious virus titers [for Δα1, P = 0.82 (day 5); P = 0.08 (day 7); for ΔBH2, P = 0.49 (day 5); P = 0.54 (day 7); unpaired t-tests] and in viral genome loads in the lungs [for Δα1, P = 0.25 (day 5); P = 0.28 (day 7); for ΔBH2, P = 0.21 (day 5); P = 0.37 (day 7); unpaired t-tests]. n.s., not significant.

Splenic infectious centers measured at 12 dpi (A, left), 14 dpi (B, left), 21 dpi (C, left), 28 dpi (D, up), 35 dpi (E, up), or 42 dpi (F, up) and viral genome load measured by real-time PCR at 12 dpi (A, right), 14 dpi (B, right), 21 dpi (C, right), 28 dpi (D, down), 35 dpi (E, down), or 42 dpi (F, down), in the BALB/c mice intranasally infected with the WT or recombinant γHV68 mutants, as indicated (Mean±SEM of five mice per group/time point/experiment). Data of 14 dpi and 28 dpi is pooled from two and three separate experiments, respectively. Preformed infectious virus was negligible in all spleen samples. No significant difference was detected at 12 dpi (A), 14 dpi (B), and 21 dpi (C) with the Δα1 and ΔBH2 mutant viruses when compared to the WT in infectious center titers [for Δα1, P = 0.58 (day 12); P = 0.75 (day 14); P = 0.18 (day 21); for ΔBH2, P = 0.64 (day 12); P = 0.73 (day 14); P = 0.81 (day 21); unpaired t-tests] and in viral genome loads [for Δα1, P = 0.85 (day 12); P = 0.76 (day 14); P = 0.96 (day 21); for ΔBH2, P = 0.56 (day 12); P = 0.73 (day 14); P = 0.25 (day 21); unpaired t-tests]. At 28 dpi (D), 35 dpi (E), and 42 dpi (F), the decreased infectious center titers (top) of vBcl-2 mutant viruses, as compared to WT γHV68, were statistically significant [vBcl-2Δα1 versus vBcl-2AAA (42 dpi), P = 0.46; vBcl-2Δα1 versus WT γHV68 (42 dpi), P = 0.08; unpaired t-tests]. At 28 dpi (D), 35 dpi (E), and 42 dpi (F), the decreased viral DNA loads (bottom) of the vBcl-2Δα1, vBcl-2AAA, and vBcl-2 null mutants, as compared to WT γHV68 and the vBcl-2ΔBH2 mutant, were statistically significant as follows (unpaired t-tests): at day 28, vBcl-2Δα1 versus WT γHV68, P<0.01; vBcl-2AAA versus WT γHV68, P<0.01; vBcl-2-null versus WT γHV68, P<0.01; vBcl-2Δα1 versus vBcl-2ΔBH2, P<0.001; vBcl-2AAA versus vBcl-2ΔBH2, P<0.001; vBcl-2-null versus vBcl-2ΔBH2, P<0.001; at day 35, vBcl-2Δα1 versus WT γHV68, P<0.05; vBcl-2AAA versus WT γHV68, P<0.05; vBcl-2Δα1 versus vBcl-2ΔBH2, P<0.01; vBcl-2AAA versus vBcl-2ΔBH2, P<0.05; at day 42, vBcl-2Δα1 versus vBcl-2ΔBH2, P<0.001; vBcl-2AAA versus vBcl-2ΔBH2, P<0.001; vBcl-2ΔBH2 versus WT γHV68, P = 0.33. I.C., infectious center. *, P<0.05; **, P<0.01; ***, P<0.001.