THE MOUSE ALBUMIN ENHANCER CONTAINS A NEGATIVE REGULATORY ELEMENT THAT INTERACTS WITH A NOVEL DNA-BINDING PROTEIN

The far-upstream mouse albumin enhancer (-10.5 to -8.43 kilobases) has both positive and negative regulatory domains which contribute the the rate and tissue specificity of albumin gene transcription. (R.S. Herbst, N. Friedman, J.E. Darnell, Jr., and L.E. Babiss, Proc. Natl. Acad. Sci. USA 86:1553-1557). In this work, the negative regulatory region has been functionally localized to sequences -8.7 to -8.43 kilobases upstream of the albumin gene cap site. In the absence of the albumin-modulating region (in which there are binding sites for the transcription factor C/EBP), the negative region can suppress a neighboring positive-acting element, thereby interfering with albumin enhancer function. The negative region is also capable of negating the positive action of the heterologous transthyretin enhancer in an orientation-independent fashion. Within this negative-acting region we can detect two DNA-binding sites, both of which are recognized by a protein present in all cell types tested. This DNA-binding activity is not competed for by any of a series of known DNA-binding sites, and hence this new protein is a candidate for a role in suppressing the albumin gene in nonhepatic cells.