We have identified a form of the pituitary-specific POU protein Pit-1 that results from deletion of the POU-specific (POUs) domain by alternative RNA splicing. This natural variant of Pit-1 (called Δ 4Pit-1) has revealed several aspects of the function of the POUs domain. The Δ 4Pit-1 protein was characterized using a Δ 4Pit-1-specific antiserum. Further, selection assays of random oligonucleotide pools identified binding site preferences for both wild type and Δ 4Pit-1. Methylation interference, copper phenanthrolene, and missing contact analyses were used to compare the binding characteristics of the two forms of Pit-1 on a selected site. DNA binding affinity assays on several DNA elements revealed that the POUs domain contains a modular DNA binding activity affecting the DNA binding affinity of the entire POU domain on some, but not on other, DNA sites. Functional analysis on such DNA elements has revealed that the POUs domain is an essential, but nonmodular, component of the Pit-1 trans-activation domain dependent on its natural context within the Pit-1 protein.
ASJC Scopus subject areas
- Molecular Biology