Analysis of regulation of polyomavirus promoters by a luciferase reporter system

The transcription factor Ying-Yang 1 (YY1), which has been shown to activate basal transcription from mouse polyomavirus (Py) late promoter, does not interact with the main viral regulatory protein, the large tumor antigen (LT) in vivo directly but via DNA (Spanielová and Velková, 2001). In this report, the role of association of YY1 with LT in regulation of the Py late promoter was studied by a luciferase reporter system. The distance between YY1 and LT binding sites in the viral regulatory region was extended by insertion of a transcriptionally inert sequence 166 nucleotides (nt) long thus making physical contact between LT and YY1 bound to their sites impossible or difficult. Analysis of viral early and late promoter activities was performed in the presence or absence of viral early tumor antigens and in the presence or absence of an inhibitor of DNA replication. The study indicated that regulation of the Py late promoter is DNA replication-linked and that association of both proteins may be involved in this type of regulation. Moreover, the plasmid DNA replication assay showed that insertion of the inert sequence between the ori-core and enhancer restricted replication of the reporter plasmid.