Biomedical subjects

Yongqing Wu

Publications and source records attributed to Yongqing Wu.

4 recordsLinked to original sources

PubMed2006

FOXP3 controls regulatory T cell function through cooperation with NFAT.

Antigen stimulation of immune cells activates the transcription factor NFAT, a key regulator of T cell activation and anergy. NFAT forms cooperative complexes with the AP-1 family of transcription factors and regulates T cell activation-associated genes. Here we show that regulatory T cell (Treg) function is mediated by an analogous cooperative complex of NFAT with the forkhead transcription factor FOXP3, a lineage specification factor for Tregs. The crystal structure of an NFAT:FOXP2:DNA complex reveals an extensive protein-protein interaction interface between NFAT and FOXP2. Structure-guided mutations of FOXP3, predicted to progressively disrupt its interaction with NFAT, interfere in a graded manner with the ability of FOXP3 to repress expression of the cytokine IL2, upregulate expression of the Treg markers CTLA4 and CD25, and confer suppressor function in a murine model of autoimmune diabetes. Thus by switching transcriptional partners, NFAT converts the acute T cell activation program into the suppressor program of Tregs.

Amino Acid Sequence↗

PubMed2006

Structure of the forkhead domain of FOXP2 bound to DNA.

FOXP (FOXP1-4) is a newly defined subfamily of the forkhead box (FOX) transcription factors. A mutation in the FOXP2 forkhead domain cosegregates with a severe speech disorder, whereas several mutations in the FOXP3 forkhead domain are linked to the IPEX syndrome in human and a similar autoimmune phenotype in mice. Here we report a 1.9 A crystal structure of the forkhead domain of human FOXP2 bound to DNA. This structure allows us to revise the previously proposed DNA recognition mechanism and provide a unifying model of DNA binding for the FOX family of proteins. Our studies also reveal that the FOXP2 forkhead domain can form a domain-swapped dimer, made possible by a strategic substitution of a highly conserved proline in conventional FOX proteins with alanine in the P subfamily. Disease-causing mutations in FOXP2 and FOXP3 map either to the DNA binding surface or the domain-swapping dimer interface, functionally corroborating the crystal structure.

Amino Acid Sequence↗

PubMed2005

Mechanism of recruitment of class II histone deacetylases by myocyte enhancer factor-2.

Class II histone deacetylases (HDACs) bind myocyte enhancer factor-2 (MEF2) and repress specific gene expression in a calcium-dependent manner. Despite their significant physiological functions in muscle, immune and neuronal cells, the mechanism of recruitment of class II HDACs by MEF2 is not well understood. Here, we have characterized the complex between the MEF2-binding motif of class II HDACs and the MADS-box/MEF2S domain of MEF2B by structural and biochemical methods. The crystal structure of a HDAC9/MEF2/DNA complex reveals that HDAC9 binds to a hydrophobic groove of the MEF2 dimer. The overall binding mode is similar to that seen in the Cabin1/MEF2/DNA complex. The detailed binding interactions at the HDAC9/MEF2 interface, however, show marked differences from those at the Cabin1/MEF2 interface. Our studies suggest a general mechanism by which class II HDACs and possibly other transcriptional co-regulators are recruited by MEF2. On the other hand, the differential binding between MEF2 and its various partners may confer specific regulatory and functional properties to MEF2 in distinct cellular processes. Such specificity provides a basis for selectively disrupting a particular MEF2/co-regulator complex by mutations or small molecules.

Adaptor Proteins, Signal Transducing↗

PubMed2003

Mutation analysis of the feedback inhibition site of phenylalanine-sensitive 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase of Escherichia coli.

In Escherichia coli, the phenylalanine-sensitive 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase (DAHPS) AroG catalyzes the first committed step in the biosynthesis of aromatic compounds. To investigate the feedback inhibition site of AroG, mutated enzymes prepared with sequence-overlap extension PCR were expressed and purified. The enzymatic activity assay showed that the amino acid replacements at Phe144, Leu175, Leu179, Phe209, Trp215Ala and Val221 completely or partially relieved feedback inhibition of AroG addressed by the phenylalanine. Ile10Ala and Delta(1-15) desensitized feedback inhibition and caused a 70 approximately 90% loss of the specific catalytic activities. These results strongly suggest an involvement of the interior region and the N-terminus of the polypeptide chain of AroG in the formation of the feedback inhibition site of DAHPS.

3-Deoxy-7-Phosphoheptulonate Synthase↗