TAP Family: Aux/IAA
Tiwari et al (2004): Aux/IAA proteins are short-lived nuclear proteins that repress expression of primary/early auxin response genes in protoplast transfection assays. Repression is thought to result from Aux/IAA proteins dimerizing with auxin response factor (ARF) transcriptional activators that reside on auxin-responsive promoter elements, referred to as AuxREs. Most Aux/IAA proteins contain four conserved domains, designated domains I, II, III, and IV. Domain II and domains III and IV play roles in protein stability and dimerization, respectively. A clear function for domain I had not been established. Results reported here indicate that domain I in Aux/IAA proteins is an active repression domain that is transferable and dominant over activation domains. An LxLxL motif within domain I is important for conferring repression. The dominance of Aux/IAA repression domains over activation domains in ARF transcriptional activators provides a plausible explanation for the repression of auxin response genes via ARF-Aux/IAA dimerization on auxin-responsive promoters.
References:
Liscum, E; Reed, JW. 2002. Genetics of Aux/IAA and ARF action in plant growth and development. Plant Mol. Biol. 49(3-4):387-400
Tiwari, SB; Hagen, G; Guilfoyle, TJ. 2004. Aux/IAA proteins contain a potent transcriptional repression domain. Plant Cell 16(2):533-43"
Tiwari, SB; Wang, XJ; Hagen, G; Guilfoyle, TJ. 2001. AUX/IAA proteins are active repressors, and their stability and activity are modulated by auxin. Plant Cell 13(12):2809-22"
