Functional analysis of chicken vimentin distal promoter regions in cultured lens cells.

Synthesis of the cytoskeletal intermediate filament protein vimentin (Vim) in the lens is unexpected due to the mesenchymal preference of Vim-encoding gene (Vim) expression and the epithelial origin of the lens. Previous studies indicated that chicken Vim gene expression in cultured lens cells is regulated by both positive- and negative-acting sequence elements within the first -767 nucleotides (nt) of its promoter. Here, we demonstrate the existence of additional upstream chicken Vim promoter elements which function in transfected lens cells. Sequences within the nt -1360/-1156 region repressed promoter activity in transfected lens cells to levels lower than that observed for the previously defined more proximal repressor elements. The -1612/-1360 region activated promoter activity to levels similar to those observed for the strongest previously defined proximal promoter. The nt sequence analysis of the upstream promoter region revealed the presence of multiple consensus repressor and activator transcription-factor-binding sites. Several of these sites have been implicated for lens expression of enzyme-crystallin-encoding genes (cry), suggesting that Vim expression may share features with the cry genes for recruitment and high-level expression in the lens.