EGF and infection: Finally, in order to demonstrate that miR-US5-2 regulation of UL138 protein expression operates through modulation of EGR1 levels during infection, we transfected human fibroblasts with negative-control miRNA, miR-US5-2 mimic, or siRNAs targeting GAB1 or EGR1 followed by infection with WT virus or a ΔEGR-1 mutant virus where an EGR1 binding site upstream of the UL138 transcriptional start site, previously shown to regulate UL138 expression in response to EGF, was mutated (14).