Activating Transcription Factor 1 and cyclic AMP response element binding protein: Characterization and analysis of contributions to transformation

Activating Transcription Factor 1 (ATF1) and cyclic AMP Response Element Binding protein (CREB) are cyclic AMP inducible transcription factors responsible for the activation of genes in response to extracellular signals. ATF1 is differentially expressed during embryogenesis and is aberrantly expressed in transformed cells. An anti-ATF1 antibody possessing inhibitory activity was cloned and expressed intracellularly as a single chain Fv fragment (scFv) to target ATF1 activity. It is hypothesized that the normal roles of ATF1 and its contribution to transformation can be determined through the selective inhibition of intracellular ATF1. Studies have been performed to investigate the roles of ATF1 in cell function and transcriptional activation. The expression of intracellular scFv results in the inhibition of ATF1 activation of CRE containing luciferase reporter constructs. Endogenous cellular proteins that are regulated by CREs located in their promoters are also decreased in the presence of the scFv. Therefore the role of ATF1 in the maintenance of expression of these genes is better understood. Additional studies focused on the role of ATF1 in neoplasia. ATF1 is directly related to malignant melanoma of soft parts (MMSP) due to a chromosomal translocation that fuses the amino terminal of the Ewings Sarcoma protein (EWS) to the carboxyl terminal of ATF1, resulting in the generation of the chimeric oncoprotein, EWS/ATF1. The scFv when expressed in MMSP cells causes a loss of viability and induces apoptosis. The scFv demonstrates the EWS/ATF1 is a causative agent in MMSP transformation, and provides preliminary evidence for a new approach to chemotherapy through the targeting of transcription factors.