IDENTIFICATION OF MULTIPLE RABBIT FLAVIN-CONTAINING MONOOXYGENASE FORM-1 (FMO1) GENE PROMOTERS AND OBSERVATION OF TISSUE-SPECIFIC DNASE-I HYPERSENSITIVE SITES

We have cloned and partially characterized the rabbit FMO1 gene as a f irst approach to understanding mechanisms controlling its tissue-speci fic expression, The isolated clones contain 14 kb of 5' flanking infor mation and approximately 30 kb of the structural gene, but do not incl ude the 3'-end. Two upstream exons were defined, both encoding 5' lead er information, The first exon, termed exon 0, contains information no t previously reported, The second exon, termed exon 1, contains inform ation previously reported for the rabbit FMO1 cDNA, Protein coding inf ormation begins seven nucleotides from the start of exon 2, A single t ranscription start site was localized in exon 1, while a cluster of si tes were defined in exon 0, consistent with two alternative promoters. Transcripts initiating in exon 0 do not contain exon 1 information du e to alternative processing and represent the major FMO1 mRNA. Neither promoter contains a TATA box or GC islands, although the exon 1 promo ter does share some sequence identity with initiator-type elements. Ho mologous sequences to several known transcription factor binding sites were found in the upstream region of the FMO1 promoters, Both promote rs were active in directing luciferase expression when transiently tra nsfected into human HepG2 cells, although the data are consistent with both requiring upstream enhancer sequences, Consistent with this obse rvation, DNase I hypersensitive sites were mapped to a 600-bp region i mmediately upstream of exon 0 using liver nuclei, No such sites were d etected with nuclei from lung. Differential DNA methylation also was n ot observed between these two tissues. (C) 1996 Academic Press, Inc.