A CRITICAL ROLE OF SP1-RELATED AND ETS-RELATED TRANSCRIPTION FACTORS IN MAINTAINING CTL-SPECIFIC EXPRESSION OF THE MOUSE PERFORIN GENE

This study was designed to determine the potential cis-elements involv ed in transcriptional regulation of the mouse perforin gene. DNase I h ypersensitive site (DHS) mapping revealed that the perforin locus cont ained six DHS within 7.0 kb of the 5' upstream sequence (-7.0 kb) and two DHS in intron 2. The six 5' upstream and one intronic DHS were det ected in only perforin-expressing lymphocytes. Chloramphenicol acetylt ransferase (CAT) activities directed by 5' upstream promoter were dete cted preferentially in perforin-expressing cell lines. A construct ter med PFP5a containing -795 bp exhibited the highest CAT activity, and P FP9a20 containing only -73 bp also produced significantly high CAT act ivity in CTLL-R8 cells. The proximal region in PFP9a20 contained two p otential Spl binding sites (GC box and CT box) and one Ets binding sit e (EBS). Electrophoretic mobility shift assay showed that each of the cis-elements bound specific protein factors. When single-point mutatio n was introduced to each GC box, EBS, and GT box in PFP9a20, at least S-fold less CAT activity was observed in CTLL-R8 cells. To confirm the importance of the three cis-acting elements in the perforin gene expr ession, point mutation was introduced again to each proximal CC box, E BS, and GT box of PFP5a. The point mutations resulted in a 2.5- to 3-f old reduction of CAT activity. The results suggest that a combination of the three proximal cis-acting elements may constitute a minimal reg ion responsible for CTL-specific expression of perforin.