TREB5

This protein is a transcription factor that regulates MHC class II genes by binding to a promoter element referred to as an X box. The protein contains two domains commonly found in transcription factors that confer DNA binding and dimerization capability. This gene product was also separately identified as a cellular transcription factor that binds to an enhancer in the promoter of the T cell leukemia virus type 1 promoter. It may increase expression of viral proteins by acting as the DNA binding partner of a viral transactivator. There is also a recent finding that the same agents that cause an ER stress response, the unfolded protein response, also increase transcription of this gene. This increase in transcription requires an ER stress response consensus binding element in the promoter. Adding to the list of functional possibilities is a recent report from studies of knockout mice showing that this gene is essential for hepatocyte growth. A pseudogene has been identified and localized to chromosome 5.