To further support our findings, mRNA extracted from KSHVinfected HEK293 cells were subjected to quantitative real-time PCR (qRT-PCR) analysis in order to evaluate egr-1 and ORF50 transcriptional activity. Uninfected cells (0 hPI) did not show detectable ORF50 expression (Fig. 3B ). On the other hand, a low baseline level of egr-1 expression was observed in the uninfected samples ( Fig. 3B ). With the onset of a primary infection, expression levels of both egr-1 and ORF50 increased up to 6hPI (Fig. 3B ). These elevated levels of egr-1 and ORF50 decreased substantially by 12-24 hPI (Fig. 3B ). No significant changes in the expression of the internal control gene encoding M6PR was observed indicating specificity of the results (data not shown). Taken together, the expression profiles of Egr-1 and RTA seem to follow an identical pattern during primary infection of cells.