Formation of the RFX gene regulatory complex induces folding of the interaction domain of RFXAP.
Major histocompatibility complex class II (MHCII) molecules have a central role in the mammalian adaptive immune response against infection. The level of the immune response is directly related to the concentration of MHCII molecules in the cell, which have a central role in initiating the immune response. MHCII molecules are therefore a potential target for the development of immunosuppressant drugs for the treatment of organ transplant rejection and autoimmune disease. The expression of MHCII molecules is regulated by a cell specific multiprotein complex. The RFX complex is the key DNA binding component of this complex. The RFX complex is composed of three proteins-RFX5, RFXAP, and RFXB-all of which are required for activation of expression of the MHCII genes. Little is currently known about the precise regions of the RFX proteins that are required for complex formation, or their structure. We have therefore identified the key regions of RFX5, RFXAP, and RFXB, which are required to form the RFX complex and have characterized the individual domains and the complexes they form using NMR and circular dichroism spectroscopy and isothermal titration calorimetry. Our results support a model for the assembly of the RFX complex in which the interaction between RFX5 and RFXAP promote folding of a poorly structured region ofRFXAP, which is required for high affinity binding of RFXB to the RFX5.RFXAP complex.
Briggs
LaTese
L
Broad Institute of Harvard and MIT, Cambridge, Massachusetts 02141, USA.
Laird
Kholiswa
K
Boss
Jeremy M
JM
Garvie
Colin W
CW
D002151:Calorimetry; D002942:Circular Dichroism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D005822:Genetic Vectors; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D016297:Mutagenesis, Site-Directed; D016133:Polymerase Chain Reaction; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
D004268:DNA-Binding Proteins; C093524:RFX5 protein, human; C413004:RFXAP protein, human; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors