Fig. 5: Histone H1 occupies multiple EBV genomic elements.

a Immunoblot analysis of WCL from Cas9+ P3HR-1 cells expressing control, H1.2, and/or H1.4 sgRNAs. b Immunoblot analysis of WCL from Cas9+ MUTU I cells expressing V5-tagged GFP, H1.2, H1.4, or H3 cDNA and subsequently control or SFPQ sgRNAs. c Schematic of the H1.2 ChIP-qPCR assay. For clarity, nucleosomes are not shown. d–f ChIP-qPCR analysis of H1.2 occupancy at the EBV (d) BZLF1 promoter, (e) oriLyt^L enhancer, and (f) oriLyt^R enhancer at 0, 6, and 24 h post 4-HT-induced lytic reactivation in Cas9+ P3HR-1 cells. These cells express the EBV immediate early proteins BZLF1 and BRLF1 fused to a modified estrogen receptor binding domain specific for 4-HT (P3HR-1 ZHT/RHT cells). 4-HT addition triggers BZLF1 and BRLF1 nuclear translocation and early gene expression. Mean ± standard deviation from n = 3 biological replicates is shown. *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001, ****p ≤ 0.0001 were calculated by one-way ANOVA. g Heatmap analysis of log₂(fold change) of histone mRNA abundance from RNA-seq analysis (GEO GSE240008) of MUTU I cells triggered for lytic reactivation by electroporation of a BZLF1 expression vector for the indicated times, relative to levels in cells electroporated for the same times with a GFP negative control expression vector. The values shown are for histones whose abundance was significantly decreased by SFPQ depletion in the RNA-seq analysis shown in Fig. 3. Histones are clustered by histone type. h Log₂(fold change) of histone protein abundance in P3HR-1 ZHT/RHT cells triggered for lytic reactivation by 4-HT for the indicated times, relative to levels in mock-induced cells⁵⁶. The values shown are for histones whose transcripts were significantly decreased in abundance upon SFPQ depletion, relative to control levels, in the RNA-seq analysis shown in Fig. 3. Histones are clustered by histone type. Representative immunoblots from n = 3 biological replicates and densitometry quantification with values normalized to the loading control GAPDH are shown. Source data are provided as a Source Data file.