title: Transcription factor Sp1 activates involucrin promoter activity in non-epithelial cell types.
abstract: The gene for human involucrin (hINV) is selectively expressed in stratifying epithelial cells lining external body surfaces. Previously, we characterized the hINV promoter 5' distal regulatory region (DRR) located between nt -2473 and -2088 upstream of the transcription start site. This region is required for optimal hINV gene expression. The DRR contains weak and strong activator elements. The strong activator comprises AP1- and Sp1-binding sites that combine to drive high-level promoter expression in human keratinocytes. Here we show that the hINV promoter is expressed in a cell-specific manner in vitro and that the DRR contains elements that are partly responsible for cell-type-specific expression of hINV. hINV promoter activity is barely detectable in 3T3 fibroblasts or HEK-293 human embryonic kidney cells. Reporter plasmids containing the full-length promoter or the isolated DRR can, however, be activated in 3T3 and HEK-293 cells by co-transfection with a plasmid encoding the transcription factor Sp1. Consistently with the lower hINV promoter activity, immunoblotting studies indicate that Sp1 protein levels are lower in 3T3 and HEK-293 cells than in human epidermal keratinocytes. Increased Sp1 protein in transfected 3T3 cells and HEK-293 cells correlates with increased promoter activity. In addition, Sp1 transfection activates the expression of the endogenous gene for hINV in HEK-293 cells. These studies suggest that Sp1 might have a role in cell-specific expression of hINV.
authors.affiliation: Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, 2109 Adelbert Road, Cleveland, OH 44106-4970, USA.
authors.forename: E B
authors.initials: EB
authors.lastname: Banks
authors.forename: J F
authors.initials: JF
authors.lastname: Crish
authors.forename: R L
authors.initials: RL
authors.lastname: Eckert
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D016384:Consensus Sequence; D000078404:Epidermal Cells; D004817:Epidermis / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D051379:Mice; D011401:Promoter Regions, Genetic; D011498:Protein Precursors / Q000235:genetics* / Q000378:metabolism; D016329:Sp1 Transcription Factor / Q000096:biosynthesis / Q000378:metabolism*; D014162:Transfection
chemical_list: D011498:Protein Precursors; D016329:Sp1 Transcription Factor; C032253:involucrin