INVOLVEMENT OF THE CYCLIC AMP-RESPONSIVE ELEMENT-BINDING PROTEIN IN BOVINE LEUKEMIA-VIRUS EXPRESSION IN-VIVO

The TAR element (Tax-responsive element; also called TxRE) is a major determinant of the regulation of bovine leukemia virus (BLV) expressio n. In order to gain insight into the mechanisms of viral expression, c omplexes formed between proteins and the TAR enhancer DNA were analyze d by gel retardation assays. We report here that nuclear lysates from ex vivo-isolated B lymphocytes contain proteins that specifically bind to TAR. An antibody directed toward the cyclic AMP-responsive element binding (CREB) protein supershifted a complex (C1) present only in BL V-infected B lymphocytes. The CREB protein thus appears to be a major transcription factor involved in BLV expression in vivo.