ACTR coactivator

A particularly intriguing example occurs in the complex of the interaction domain of ACTR and the nuclear coactivator binding domain (NCBD) of CBP. CD spectra show that although neither of the free proteins is cooperatively folded, the complex is folded and stable. The 3D structure of the complex [23] demonstrates one of the rationales for the existence of intrinsically unstructured proteins the surface area of contact between the two proteins (Fig. 6.5) is much larger than could be expected from the interaction of folded proteins of comparable size, as has been pointed out [29]. 

ACTR/RAC3 and p/cip A receptor-associated cofactor 3 (RAC3) was cloned as a coactivator for the liganded receptor LBD (69) and found to be identical to another coactivator named ACTR, which was known to possess intrinsic HAT activity (70). Sequence comparison revealed a homology to the SRC-1 and TIFII members (69) therefore, it was also categorized in the SRC family. A closely related coactivator, the p300/CBP cointegrator associated protein (p/CIP), was found to interact with CBP and was required for the actions of CBP-dependent transcription factors (71). These members represent the third SRC family that functions as coactivators for RARs and RXRs, and possesses HAT activity. 

Chen H, Lin RJ, Schiltz RL, Chakravarti D, Nash A, et al. 1997. Nuclear receptor coactivator ACTR is a novel his-... 

The pl60 family of coactivators including steroid receptor coactivator 1 (SRC-1), TIF/GRIP (SRC-2), and ACTR/pCIP (SRC-3) [24] stimulates the transcriptional activity of nuclear receptors. The pi60 family of coactivators has three LXXLL motifs in the receptor-interacting domain (RID) that interacts with the AF-2 domain of nuclear receptors. SRC-1 is a weak HAT that interacts with p300/CBP and recruits CARM-1. 

Activity is also influenced by families of intermediary proteins that bind to AF-2 domains of the receptors and function as coactivators or corepressors of gene transcription [30, 31] Coactivators of retinoid-induced gene transcription include SRC-l/NCoA-1, TIF2/GRIP-1/ NCoA-2, and PCIP/ACTR/AIB1. Corepressor proteins include N-CoR, SMRT, and TRIP [32-36]. 

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