A Structural Basis for BRD2/4-Mediated Host Chromatin Interaction and Oligomer Assembly of Kaposi Sarcoma-Associated Herpesvirus and Murine Gammaherpesvirus LANA Proteins
Figure 5
Role of the ‘Basic top’ of LANA in BET Protein Interaction and Oligomerization.
A: Co-IP of kLANA ‘basic top’ mutants with GFP-BRD4 (left) and GFP-BRD2 (right). Panels I–IV as in Figure 4B. ‘09A/38A’: K1109A/K1138A mutant. B: Oligomerization assay with kLANA ‘basic top’ mutants. Upper top: WB detecting FL kLANA wt or mutants bound to GST-kLANA wt or mutant CTDs. Lower top: same WB membrane as above detecting GST-LANA CTD proteins. (e.v.) empty vector, (-) GST alone, (MUT) mutant GST-LANA CTD corresponding to the FL LANA mutant indicated above. Bottom: Expression of FL LANA proteins and the actin control. C: EMSA with LBS1+2 oligonucleotide and GST-LANA(934-1162) ‘basic top’ mutants. (wt+comp.) control with 10× excess of unlabeled probe. Below: Expression of the GST-LANA CTD proteins (Coomassie stain). D: Transient replication assay with kLANA ‘basic top’ mutants and pTR1 vector in HeLa cells (performed in duplicates). Panel I: Southern blot of replicated DNA, remaining after digest with KpnI and DpnI. Panel II: Southern blot of input DNA linearized with KpnI; pBluescript (pBS) does not replicate (internal control). (-) empty vector control. Panel III: LANA expression. Panel IV: Actin control. E: Top view of kLANA and mLANA CTDs. Mutated residues are labeled. F: Co-IP of GFP-BRD4 (left) and GFP-BRD2 (right) with HA-mLANA wt or 4A mutant. Panels I: Immunoblot of co-IP samples detecting GFP-BET proteins. Panels II: Blot of the same samples detecting HA-mLANA. Panels III: Expression of BET proteins. Panels IV: Actin loading control. G: C57BL/6 mice were infected i.n. with the MHV68 wt, the mLANA: 4A (‘4A’) and STOP (‘73-STOP’) mutant viruses and respective revertants (‘4A rev’), (‘73-STOP rev’). DNA isolated from splenocytes was used for qPCR analysis. Marks represent individual mice and the bars the means. Data include two independent experiments. (***) P<0.001. H: Ex vivo reactivation assay with the splenocyte samples from (G). Dashed line: the point of 63.2% reactivation (MOI = 1).