1: Int Immunol. 2003 Apr;15(4):467-75. 

MHC class II enhanceosome: how is the class II transactivator recruited to
DNA-bound activators?

Jabrane-Ferrat N, Nekrep N, Tosi G, Esserman L, Peterlin BM.

Department of Surgery and Comprehensive Cancer Center, University of California
San Francisco, CA 94115-0703, USA.

MHC class II (MHCII) determinants play a crucial role in the immune response by
presenting antigenic peptides to T cells. Their expression is controlled from
compact promoters at the transcriptional level. Pre-assembled regulatory factor
X (RFX) and nuclear factor Y (NFY) complexes form a platform on DNA. The class
II transactivator (CIITA) can then be recruited through multiple protein-protein
interactions. In this report, we defined domains of CIITA that are responsible
for its interactions with these DNA-bound factors. Furthermore, using
DNA-affinity precipitation, we demonstrated that although CIITA binds at least
five activators, RFX5, RFXAP, RFXANK/B, NFYB and NFYC, its assembly on the
promoter requires the addition of nuclear extracts. We conclude that not only
does the platform bind DNA via multiple, spatially constrained nteractions, but
that it can recruit only modified and/or complexed CIITA to MHCII promoters.

PMID: 12663676 [PubMed - indexed for MEDLINE]


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2: Mol Cell Biol. 2002 Aug;22(15):5616-25. 

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

Jabrane-Ferrat N, Nekrep N, Tosi G, Esserman LJ, Peterlin BM.

Department of Surgery, University of California-San Francisco, San Francisco, CA
94115-0703, USA.

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.

PMID: 12101253 [PubMed - indexed for MEDLINE]


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