Identification of a Nuclear Respiratory Factor-1 Binding Site within the Core Promoter of the human polio virus receptor/CD155 Gene

Abstract

In this report we describe a cis-acting element within the core promoter of the CD155 gene specifying the polio virus receptor that is bound by the nuclear respiratory factor-1 (NRF-1) transcription factor. DNase I footprint analysis identified a nuclear protein binding site from -282 to -264 nucleotides upstream of the translation initiation codon of the CD155 gene, which we have called foot print IV (FPIV). Linker scanning mutagenesis revealed that a tandem repeat motif, GCGCAGGCGCAG, located within FPIV was essential for the basal activity of the CD155 core promoter. The results of the electrophoretic mobility shift assay experiments suggested that identical FPIV binding activities were present in a variety of nuclear extracts and that the tandem repeat was essential for binding. A one-hybrid screen was then carried out using FPIV as bait to clone the cDNA of the FPIV binding factor. The sequences of the cDNAs that were cloned from the screen were identical to NRF-1, a result that was confirmed by further electrophoretic mobility shift assay experiments. Overexpression of full-length NRF-1 and a dominant-negative form of NRF-1 modulated reporter gene expression driven by the core promoter. Remarkably, CD155 is the first gene shown to be regulated by NRF-1 that possesses an expression profile during embryogenesis correlating with this factor's proposed role in the development of the vertebrate optic system. We propose that NRF-1, which has been shown by others to be expressed during embryogenesis in animal systems, may be involved in regulating the expression of CD155 at specific stages of central nervous system development.