Y. Tsutsumi-ishii et al., Role of CCAAT/enhancer-binding protein site in transcription of human neutrophil peptide-1 and-3 defensin genes, J IMMUNOL, 164(6), 2000, pp. 3264-3273
The human neutrophil defensins (human neutrophil peptides (HNPs)), major co
mponents of azurophilic granules, contribute to innate and acquired host im
munities through their potent antimicrobial activities and ability to activ
ate T cells. Despite being encoded by nearly identical genes, HNP-1 is more
abundant in the granules than HNP-3. We investigated the regulation of HNP
-1 and HNP-3 expression at the transcriptional level using a promyelocytic
HL-60 cell line. Luciferase analysis showed that transcriptional levels of
HNP-1 and HNP-3 promoters were equivalent and that an similar to 200-bp reg
ion identical between promoters was sufficient for transcriptional activity
. Furthermore, overlapping CCAAT/enhancer-binding protein (C/EBP) and c-Myb
sites in the region were found to be required for efficient transcription.
Gel mobility shift assay demonstrated that C/EBP alpha predominantly bound
to the C/EBP/c-Myb sites using HL-60 nuclear extracts. No specific binding
to C/EBP/c-Myb sites was observed in nuclear extracts from mature neutroph
ils, which expressed neither C/EBPa: protein nor HNP mRNAs. Taken together,
these findings suggest that the difference in the amounts of HNP-1 and HNP
-3 and that C/EBP alpha plays an important role in the transcription peptid
es in neutrophils is caused by posttranscriptional regulation of HNP genes
in immature myeloid cells.