Inducible transcriptional activity of bcn-1 element from laminin γ1-chain gene promoter in renal and nonrenal cells

Laminin is a major component of the extracellular matrix whose expression is regulated by growth factors. The laminin gamma 1-chain promoter contains a newly identified transcriptional element denoted bcn-1 that is both active and inducible in mesangial cells. In this study: we explored activation of the bcn-1 element in other renal and nonrenal cells. Treatment of rat glomerular epithelial cells (GEC) with phorbol 12-myristate 13-acetate (PMA) increased activity of the bcn-1 transcriptional element, within the context of the native laminin yl-chain promoter or when cloned upstream of a heterologous promoter. Treatment of GEC with PMA induced nuclear DNA-binding activity, BCN-1, which was recognized by the bcn-1 motif in a gel shift assay. These results provide evidence that the bcn-1 motif and its cognate BCN-1 factor(s) may regulate transcription of the laminin yl-chain in GEC. The bcn-1 element and its cognate BCN-1 DNA-binding activity were also inducible in monkey kidney COS-7 and in human T cell Jurkat lines. SDS-PAGE of in situ ultraviolet cross-linked nucleoproteins from GEC, COS, and Jurkat cells revealed one major 110-115 kDa adduct in all three cell lines. These results demonstrate that the bcn-1 element is active in renal and nonrenal cells from different mammalian species where the same protein contributes to the inducible BCN-1 DNA-binding activity.