Site-directed mutagenesis of a region of the PK-R promoter spanning nts −91 to −78 identifies the core motif CTCTG of a novel PK-R regulatory element (PKR-RE1).

PK-R promoter reporter gene constructs harboring mutations from nts −91 to −78 were expressed in K562 cells. The applicable mutation is depicted in the lower part of the figure. Luciferase activities were calculated relative to control pGL3-SV40. pGL3-Basic was included as a negative (promoterless) control. The decreased promoter activity as a result of the introduced mutations at nts −87 to −83 revealed a single pentanucleotide motif CTCTG. * Statistically significant (P < .05).