Nuclear receptors: from the nucleus to the cytoplasm

Abstract

Nuclear receptors (RNs) are a family of transcription factors activated by ligand which regulate the expression of many genes dependent on the cellular type and context. The subcellular localization of RNs is highly dynamic and affects its function as transcriptional factors. In the presence of its specific ligand, the RNs increase in the nucleus to modulate the expression of their target genes. Thus, the exit from nucleus to cytoplasm of RNs decreases its nuclear accumulation and its transcriptional activity. Therefore, nuclear export is an important mechanism regulating the activity of RNs. Despite its importance, the process of nuclear export of RNs has not been fully studied. However, the studies made so far suggest the involvement of the CRM–1 and Calreticulin (CRT) proteins as mediators of this process. In this review, we highlight the nuclear export as a regulatory mechanism to control the functions of RNs and the structural and functional characteristics of CRM–1 and CRT exportins are discussed.