Nuclear Factor 1 Interacts with Five DNA Elements in the Promoter Region of the Human Cytomegalovirus Major Immediate Early Gene

The human cytomegalovirus (HCMV), a ubiquitous pathogen of the herpesvirus group, has a linear double-stranded DNA genome of 235 kb. The expression of its major immediate early gene (IE1) is entirely dependent on host factors, presumably proteins binding to DNA elements in the regulatory regions of the gene. We have identified four high-affinity binding sites for nuclear factor 1 (NF1) in the promoter upstream region of IE1 gene between nucleotides -780 and -610, and an additional, even stronger, binding site in the first intron near nucleotide +350. NF1 activity is found in a wide range of species and binds to the sequence 5' TGGC/ANNNNNGCCAA3' on double-stranded DNA, protecting approximately 25 bp from DNase I digestion; its functional importance has been found first in the necessity for adenovirus DNA replication, where it may be important in mediating the binding of other proteins. The regulatory significance of NF1 recognition elements within other genes is unknown. The NF1 binding sites in the HCMV IE1 gene coincide with regions that had been shown to be sensitive to DNase I in the active gene but not sensitive in the silent gene; there was, however, no NF1 binding in the strong and constitutively DNase I-hypersensitive transcription enhancer of the IE1 gene. This suggests that the specific protein--DNA interaction described is important in the regulated control of the IE1 gene.