Inhibition of XPB ATPase activity blocks EBV lytic mRNA synthesis. (A) BrU incorporation assay to measure the effect of TPL on transcription initiation. EBV lytic replication in AGSiZ cells was induced (+ind.) by addition of doxycycline and either mock-treated or treated with SPR. Forty-eight hours postinduction, cells were treated with TPL for 1 h and then pulsed with BrU for 30 min. Newly synthesized RNA was immunoprecipitated with anti-BrU antibody and analyzed by qRT-PCR. (A) SM-dependent genes (BILF2, BDLF1, and BcLF1). (B) SM-independent genes (BALF2, BDLF4, BALF4, and BBRF2). (C) Cellular genes (actin GAPDH, NFKBIA, and IL-8). (D) Efficacy of XPB depletion by SPR. Western blots were performed with protein samples above and blotted with anti-XPB and anti-SM antibody. The blot was stripped and reprobed with antitubulin as a loading control. The error bars indicate the SEM from three replicates. All reductions in transcription initiation due to TPL were significant with a P value from 0.009 to 0.02.