BLIMP1α up-regulates BZLF1 expression and induces lytic cycle in LCLs. (A) Quantitative RT-PCR analysis of BZLF1 mRNA levels in OKU-LCL after transfection with BLIMP1α or empty vector. In all transfected LCLs (n = 5, Table 1), the expression of BLIMP1α was followed by the up-regulation of BZLF1 mRNA. (Left panel) Immunostaining revealed that ectopic BLIMP1α expression increased the frequency of BZLF1-expressing cells. (B) Ectopic expression of BLIMP1α led to the increased expression at 24 and 48 hours of BRLF1, and of the lytic cycle genes, BMLF1, BNLF2a, and BALF4. Shown here are results of OKU-LCL; similar results were obtained after transfection of SAL-LCL and B95.8 cells (data not shown). Image is at magnification of ×450, and was acquired with 60×/1.40 NA oil immersion objective lens (Nikon Ltd).