SITE-DIRECTED MUTAGENESIS REVEALS A LIVER TRANSCRIPTION FACTOR ESSENTIAL FOR THE ALBUMIN TRANSCRIPTIONAL ENHANCER

A method based on the polymerase chain reaction is described for constructing a clustered set of base-pair changes, deletions, or insertions at any site on a DNA fragment. Advantages of the procedure are that virtually every product has the desired sequence alteration and that only a single round of polymerase chain reaction is required. We used this method to demonstrate that the binding of a specific liver nuclear protein, which we call eH-TF, is essential for the function of the enhancer element of the mouse albumin gene. The eH-TF binding activity is hepatocyte-specific; it binds to a functional region of the albumin promoter and is distinct from other albumin promoter factors, and part of the eH-TF binding sequence, TGTTTGC, occurs in functional regulatory sites of other liver-specific genes.