Relationship between an enhancer element in the human antithrombin III gene and an immunoglobulin light-chain gene enhancer

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Abstract
Enhancers, cis-acting transcriptional control elements have been described in both viral and cellular genes. They influence transcription in a quantitative fashion, act over relatively large distances (several kilobases, kb) and behave independently of their position and orientation. Enhancers have been described in immunoglobulin, chymotrypsin and insulin genes. They bear little homology with each other except for an 8-base pair (bp) 'consensus' core element, GTGGAAATTTG (refs 10, 11), but even this element is sometimes non-homologous. I have searched for such elements in the human antithrombin III (AT-III) gene. AT-III is an important coagulation protein which inactivates thrombin. It is produced by the liver and, to a lesser extent, by the kidney. Here, I report that the 5' flanking region of the AT-III gene encodes a segment homologous with the enhancer containing the joining-constant kappa (J kappa-C kappa) intron of immunoglobulin kappa-chain genes. This extensive homology suggests the existence of regulatory factors that recognize common DNA sequences in lymphoid tissues and in those which express AT-III.