Structure, chromosomal localization, and promoter analysis of the human elastin microfibril interfase located protein (EMILIN) gene

Elastin microfibril interfase-located protein (EMILIN) is an extracellular matrix glycoprotein abundantly expressed in elastin-rich tissues such as th e blood vessels, skin, heart, and lung. It occurs with elastic fibers at th e interface between amorphous elastin and microfibrils. In vitro experiment s suggested a role for EMILIN in the process of elastin deposition. This mu ltimodular protein consists of 995 amino acids; the domain organization inc ludes a C1q-like globular domain at the C terminus, a short collagenous sta lk, a region containing two leucine zippers, and at least four heptad repea ts with a high potential for forming coiled-coil alpha-helices and, at the N terminus, a cysteine-rich sequence characterized by a partial epidermal g rowth factor-like motif and homologous to a region of multimerin. Here we r eport the complete characterization of the human and murine EMILIN gene, th eir chromosomal assignment, and preliminary functional data of the human pr omoter, A cDNA probe corresponding to the C terminus of EMILIN was used to isolate two genomic clones from a human BAC library. Sequencing of several derived subclones allowed the characterization of the whole gene that was f ound to be about 8 kilobases in size and to contain 8 exons and 7 introns, The internal exons range in size from 17 base pairs to 1929 base pairs. All internal intron/exon junctions are defined by canonical splice donor and a cceptor sites, and the different domains potentially involved in the format ion of a coiled-coil structure are clustered in the largest exon, The 3'-en d of the EMILIN gene overlaps with the 5'-end of the promoter region of the ketohexokinase gene, whose chromosomal position is between markers D2S305 and D2S165 on chromosome 2. A 1600-base pair-long sequence upstream of the translation starting point was evaluated for its promoter activity; five de letion constructs were assayed after transfection in primary chicken fibrob lasts and in a human rhabdomyosarcoma cell line. This analysis indicates th e existence of two contiguous regions able to modulate luciferase expressio n in both cell types used, one with a strong activatory function, ranging f rom positions -204 to -503, and the other, ranging from positions -504 to - 683, with a strong inhibitory function.