The protein encoded by this gene is a leucine zipper-containing transcriptional coactivator that may link the upstream activator ATF2 with the basal transcription complex. The encoded protein is closely associated with chromatin and is required for the proper differentiation of embryonic carcinoma and embryonic stem cells. Found nearly exclusively in pluripotent cells, this protein can also serve as a transcriptional repressor. [provided by RefSeq, Nov 2015].