Major histocompatibility complex class II (MHC-II) genes are regulated in a B-cell-specific and gamma interferon-inducible manner. Conserved upstream sequences (CUS) in their compact promoters bind nuclear factor Y (NFY) and regulatory factor X (RFX) complexes. These DNA-bound proteins form a platform that attracts the class II transactivator, which initiates and elongates MHC-II transcription. In this report, we analyzed the complex assembly of these DNA-bound proteins. First, we found that NFY can interact with RFX in cells. In particular, NFYA and NFYC bound RFXANK/B in vitro. Next, RFX5 formed dimers in vivo and in vitro. Within a leucine-rich stretch N-terminal to the DNA-binding domain in RFX5, the leucine at position 66 was found to be critical for this self-association. Mutant RFX5 proteins that could not form dimers also did not support the formation of higher-order DNA-protein complexes on CUS in vitro or MHC-II transcription in vivo. We conclude that the MHC-II transcriptional platform begins to assemble off CUS and then binds DNA via multiple, spatially constrained interactions. These findings offer one explanation of why in the Bare Lymphocyte Syndrome, which is a congenital severe combined immunodeficiency, MHC-II promoters are bare when any subunit of RFX is mutated or missing.

Major histocompatibility complex class II transcriptional platform: assembly of nuclear factor Y and regulatory factor X (RFX) on DNA requires RFX5 dimers

TOSI, GIOVANNA;
2002-01-01

Abstract

Major histocompatibility complex class II (MHC-II) genes are regulated in a B-cell-specific and gamma interferon-inducible manner. Conserved upstream sequences (CUS) in their compact promoters bind nuclear factor Y (NFY) and regulatory factor X (RFX) complexes. These DNA-bound proteins form a platform that attracts the class II transactivator, which initiates and elongates MHC-II transcription. In this report, we analyzed the complex assembly of these DNA-bound proteins. First, we found that NFY can interact with RFX in cells. In particular, NFYA and NFYC bound RFXANK/B in vitro. Next, RFX5 formed dimers in vivo and in vitro. Within a leucine-rich stretch N-terminal to the DNA-binding domain in RFX5, the leucine at position 66 was found to be critical for this self-association. Mutant RFX5 proteins that could not form dimers also did not support the formation of higher-order DNA-protein complexes on CUS in vitro or MHC-II transcription in vivo. We conclude that the MHC-II transcriptional platform begins to assemble off CUS and then binds DNA via multiple, spatially constrained interactions. These findings offer one explanation of why in the Bare Lymphocyte Syndrome, which is a congenital severe combined immunodeficiency, MHC-II promoters are bare when any subunit of RFX is mutated or missing.
2002
Jabrane, Ferrat; N., Nekrep; Tosi, Giovanna; L. J., Esserman; M. B., Peterlin
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11383/1491009
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