Nuclear mRNA export by betaherpesviral pUL69 homologs. (A) Schematic representation of the pDM128/CMV/RRE reporter plasmid. The CAT reporter gene (CAT) and the HIV-1 Rev responsive element (RRE) are localized within an intron flanked by inefficiently used HIV-1 splicing sites (5′SD and 3′SA). Also depicted are the CMV promoter (CMV-P) and the SV40 late poly(A) signal (SV40PA). (B and C) CAT mRNA export assay of pUL69 and homologous proteins. The diagram shows the relative amounts of CAT protein measured 36 h posttransfection of HEK293T (B) or NIH 3T3 (C) cells with a mixture of the reporter pDM128/CMV/RRE and plasmids expressing either FLAG-pUL69 (panel A, lane 3; panel B, lane 2) or FLAG-tagged betaherpesviral pUL69 homologs as indicated at the bottoms of the diagrams (panel A, lanes 4 to 8; panel B, lanes 3 to 7). HIV-1 Rev served as a positive control (panel A, lane 2) and pcDNA3.1 as a negative control (panels A and B, lanes 1). The relative amounts of CAT protein are given as percentages relative to that of HIV-1 Rev (panel B, lower panel) or HCMV pUL69 (panel C, lower panel), and standard deviations of at least three experiments are shown as bars.