Solution Structure of the Heterotrimeric Complex between the Interaction Domains of RFX5 and RFXAP from the RFX Gene Regulatory Complex

JOURNAL OF MOLECULAR BIOLOGY

卷:403

Article

Laird, Kholiswa M.¹  Briggs, LaTese L.¹  Boss, Jeremy M.²  Summers, Michael F.¹  Garvie, Colin W.¹ 

[1] Univ Maryland, Dept Chem & Biochem, Baltimore, MD 21250 USA

[2] Emory Univ, Sch Med, Dept Microbiol & Immunol, Atlanta, GA 30322 USA

关键词: MECII;    RFX5;    RFXAP;    enhanceosome;    gene regulation;   

DOI  :  10.1016/j.jmb.2010.08.025

来源: Elsevier

【 摘 要 】

The mammalian immune response is mediated by a heterotetrameric transcriptional control complex, called regulatory factor X (RFX), that regulates the expression of major histocompatibility complex class H genes. RFX comprises three proteins: RFX5 (two copies), RFXAP, and RFXB, and mutations and deletions that prevent the assembly of the RFX complex have been linked to a severe immunodeficiency disorder. Two RFX5 molecules and one RFXAP molecule assemble in the cytoplasm prior to nuclear localization, a process mediated by an N-terminal dimerization domain of RFX5 (RFX5(N)) and a C-terminal domain of RFXAP (RFXAP(C)). We previously presented evidence that RFXAP(C) is unstructured in the absence of RFX5(N) but adopts a regular structure in the RFX5(2)(N)_RFXAP(C) complex and that the RFX5(2)(N)_RFXAP(C) complex binds RFXB with high affinity. We now report the structure of the RFX5(2)(N)_RFXAP(C) complex, determined in solution by N-15- and C-13-edited NMR spectroscopy. RFX5(N) consists of a long central helix flanked by two shorter helices The central helices of the two RFX5(N) molecules form an antiparallel coiled coil, and the flanking helices pack at the ends of the long helices in a perpendicular arrangement such that the RFX5(N) dimer is shaped like a staple. RFXAP(C) consists of two a-helices that form a V-shaped structure that packs within the RFX5(2)(N) staple. Leucine residues in the leucine-rich region of RFX5(N) (62-LYLYLQL-68) that are critical for major histocompatibility complex class II gene expression in vivo contribute to both the dimer (Leu64 and Leu68) and the RFX5(N) _RFXAP(C) interfaces (Leu62 and Leu66). The clustering of hydrophobic residues from different regions of RFXAPc suggests a potential binding site for RFXB. (C) 2010 Elsevier Ltd All rights reserved.

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