The present invention relates to isolated human and rat nucleic acid molecules encoding a protein or polypeptide that modulates transcriptional activation in a cell with or without collaboration with a nuclear hormone receptor transcriptional co-activator. The present invention also relates to the proteins or polypeptides encoded by those nucleic acid molecules, and antibodies against such proteins or polypeptides. The present invention also relates to a variety of uses for the nucleic acid molecules, proteins or polypeptides, and the related antibodies of the present invention, including methods of: regulating cellular proliferation, differentiation, and development; modulating the activity of a transcriptional co-activator complex and a transcription factor in cells; regulating hormone receptor activity and endocrine function in cells; and treating diabetes and insulin resistance in a subject.