Tissue- and species-specific promoter elements of rat 7-crystallin genes

The 5 ' flanking regions of the six rat 7-crystallln genes (7A-7F) are all capable of conferring lens-specific expression to the bacterial chloramphenicol acetyl transferase (CAT) reporter gene in either transdifferentiating chicken neural retina cells or mouse lens epithelial cells. Deletion mapping of the most active 7-crystallin promoter region, the 7D region, showed that at least three elements are required for maximal expression in mouse lens epithelial cells: element(s) located between-200 and-106, a conserved CG rich region around position- 75, and a CG stretch around-15. The region between-200 and-106 was dispensable in transdifferentiating chicken neural retina cells, which instead required the region between-106 and- 7 8. The maximal activity of the 7E and 7F promoters was also dependent upon the integrity of the conserved CG region located around- 7 5. A synthetic ollgonucleotide containing this sequence was capable of lens-specific enhancement of the activity of the tk promoter in transdifferentiating chicken neural retina cells but not In mouse lens epithelial cells. Our results further show that this region may contain a silencer element, active in non-lens tissues, as well