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Regulatory factor X, a bare lymphocyte syndrome transcription factor, is a multimeric phosphoprotein complex
C S Moreno1, E M Rogers, J A Brown
1Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA 30322, USA.
Journal of Immunology (Baltimore, Md. : 1950)
|June 15, 1997
Summary
Regulatory factor X (RFX) is crucial for MHC class II gene transcription. Mutations in bare lymphocyte syndrome groups B and D prevent RFX complex assembly, halting class II expression.
Area of Science:
- Molecular Biology
- Immunology
- Genetics
Background:
- Regulatory factor X (RFX) is a transcription factor vital for MHC class II gene expression.
- RFX binds to the X1 box in MHC class II promoters, regulating transcription.
Purpose of the Study:
- To investigate the subunit structure of the native RFX complex.
- To determine the role of RFX complex assembly in class II expression.
- To identify the molecular basis of bare lymphocyte syndrome complementation groups B and D.
Main Methods:
- Coimmunoprecipitation using RFX5 antisera to identify RFX subunits.
- Metabolic labeling with [32P]orthophosphate to study subunit phosphorylation.
- Analysis of RFX complex in B cells and fibroblasts, including those from bare lymphocyte syndrome patients.
Main Results:
- RFX5 coimmunoprecipitated with 41 kDa and 36 kDa polypeptides, identifying them as RFX subunits.
- All RFX subunits were phosphorylated in vivo, independent of CIITA.
- The p41 and p36 subunits were absent in B cells from bare lymphocyte syndrome groups B and D, indicating failed RFX complex assembly.
Conclusions:
- RFX complex assembly is essential for MHC class II expression.
- Mutations in bare lymphocyte syndrome complementation groups B and D lead to an inability to assemble the RFX complex, thus impairing class II expression.