Abstract: The molting hormone, 20-hydroxyecdysone (20E), is an insect steroid hormone which plays a dominant role in the regulation of insect molting, metamorphosis, reproduction and other physiological processes. The 20E nuclear receptor, EcR-USP, has been identified for 20 years, and several breakthroughs have been recently made in understanding the transcriptional regulation mechanisms of 20E-cR-USP. Recent research indicates that: (1) the 20E receptor is composed of two nuclear receptor molecules, i. e., EcR and USP. (2) The EcR-USP heterodimer obtains DNA binding activity with the assistance of a molecular chaperone-containing heterocomplex. (3) 20E transcriptionally activates the EcR-USP heterodimer by releasing corepressors and recruiting co-activators. (4) The ligand-receptor complex, 20E-EcR-USP, triggers a transcriptional cascade, including transcription of the 20E primaryresponse genes and the 20E secondaryresponse genes induced by transcription factors encoded by the 20E primary-response genes, to regulate physiological and developmental events.

Key words: Ecdysone, 20-hydrxoecdysone(20E), EcR-USP, transcriptional regulation； MCH, co-repressor, co-activator, PCD