Genomic cloning, mapping, structure and promoter analysis of HEADPIN, a serpin which is down-regulated in head and neck cancer cells

Headpin is a novel serine proteinase inhibitor (serpin) that is down-regula ted in squamous cell carcinoma of the oral cavity and in squamous cell carc inoma cell lines of the head and neck. Using a panel of 18q21.3 YAC clones, we mapped and cloned the HEADPIN gene. The gene spans 10 kb and is compose d of eight exons and seven introns. The genomic structure is identical with some other ovalbumin serpins (ov-serpins) in terms of the numbers, positio n and phasing of the intron/exon boundaries. HEADPIN was mapped within the serpin cluster in 18q21.3 between MASPIN and SCCA2 as follows: cen-MASPIN-H EADPIN-SCCA2-SCCA1-tel. The transcription start site was determined and the promoter activity of the 5'-flanking region was analyzed. Luciferase promo ter assays in HaCaT cells showed that the -432 to -144 nucleotide region ha s functional promoter activity. The activity of the promoter/enhancer was n ot observed in head and neck cancer cell lines TU167 and UMSCC1 which lack headpin expression. These data suggest that the differential expression of headpin in normal and carcinoma-derived cells is regulated at the transcrip tional level. Understanding the genomic organization and transcriptional re gulation of the ov-serpins clustered within 18q21.3 provides a critical fra mework for assessing their potential role in cancer. (C) 2000 Elsevier Scie nce B.V. All rights reserved.