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Crystal structure of Myc3 N-terminal JAZ-binding domain [44-238] from Arabidopsis
Structural highlights
FunctionMYC3_ARATH Transcription factor involved in tryptophan, jasmonic acid (JA) and other stress-responsive gene regulation. With MYC2 and MYC4, controls additively subsets of JA-dependent responses. Can form complexes with all known glucosinolate-related MYBs to regulate glucosinolate biosynthesis. Binds to the G-box (5'-CACGTG-3') of promoters. Activates multiple TIFY/JAZ promoters.[1] [2] [3] [4] [5] Publication Abstract from PubMedThe plant hormone jasmonate plays crucial roles in regulating plant responses to herbivorous insects and microbial pathogens and is an important regulator of plant growth and development. Key mediators of jasmonate signalling include MYC transcription factors, which are repressed by jasmonate ZIM-domain (JAZ) transcriptional repressors in the resting state. In the presence of active jasmonate, JAZ proteins function as jasmonate co-receptors by forming a hormone-dependent complex with COI1, the F-box subunit of an SCF-type ubiquitin E3 ligase. The hormone-dependent formation of the COI1-JAZ co-receptor complex leads to ubiquitination and proteasome-dependent degradation of JAZ repressors and release of MYC proteins from transcriptional repression. The mechanism by which JAZ proteins repress MYC transcription factors and how JAZ proteins switch between the repressor function in the absence of hormone and the co-receptor function in the presence of hormone remain enigmatic. Here we show that Arabidopsis MYC3 undergoes pronounced conformational changes when bound to the conserved Jas motif of the JAZ9 repressor. The Jas motif, previously shown to bind to hormone as a partly unwound helix, forms a complete alpha-helix that displaces the amino (N)-terminal helix of MYC3 and becomes an integral part of the MYC N-terminal fold. In this position, the Jas helix competitively inhibits MYC3 interaction with the MED25 subunit of the transcriptional Mediator complex. Our structural and functional studies elucidate a dynamic molecular switch mechanism that governs the repression and activation of a major plant hormone pathway. Structural basis of JAZ repression of MYC transcription factors in jasmonate signalling.,Zhang F, Yao J, Ke J, Zhang L, Lam VQ, Xin XF, Zhou XE, Chen J, Brunzelle J, Griffin PR, Zhou M, Xu HE, Melcher K, He SY Nature. 2015 Aug 10. doi: 10.1038/nature14661. PMID:26258305[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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