Site-Specific Interaction of a Partially Purified Human Lens Factor(s) with Conserved Sequences of the Human Gamma Crystallin Gene

Abstract

In an attempt to understand the molecular mechanisms governing the cell-type-specific expression of human gamma crystallin genes we have analyzed human lens extract for the presence of factors which specifically interact with the regulatory regions. Our analyses indicate that a partially purified fraction contains an activity which specifically recognizes the proximal domain (−46 to −26) of the human gamma crystallin gene. This conserved region has been previously shown to function as a strong transcriptional activator of the mouse gamma crystallin gene. Methylation interference experiments further suggest that the factor makes contact with several G residues within this protected region. A. similar (but not necessarily identical) activity is also found to be present in HeLa cell, lens epithelial cell and retinal pigment epithelial cell extracts. However, no such activity is detectable in nonlens fibroblast extract. Further characterization of the proteins reveals that the lens factor differs in its physical properties from that of the HeLa factor. These results demonstrate the presence of a candidate regulatory factor(s) in human lens which may be directly or indirectly involved in modulating the tissue-specific expression of the human gamma crystallin gene.