Functional relationships between transcriptional control signals of the thymidine kinase gene of herpes simplex virus.

Transcriptional control signals occur at three separate locations upstream from the herpes virus thymidine kinase gene. I have used two approaches to examine how these signals function in relation to one another. First, double mutants that simultaneously mutate various pairs of transcriptional signals were constructed. Analyses of the transcriptional phenotypes of such mutants suggest that the two most distally located signals may function in the same metabolic step, whereas the proximal signal appears to function in a process distinct from that of the distal signals. Second, the distances that normally separate the three transcriptional signals were systematically altered. These condensation and expansion mutants were studied to determine to what extent the spatial relationship between the signals is important to their function. The transcriptional phenotypes of these spacing-change mutants show that the amount of DNA that separates the three transcriptional signals is not rigidly fixed.