title: Forkhead transcription factor FOXP3 upregulates CD25 expression through cooperation with RelA/NF-κB.
abstract: Considerable evidence supports the prediction that CD25 is directly regulated by the forkhead transcription factor FOXP3. However, given that CD25 is normally upregulated in activated T cells, regardless of whether they express FOXP3, this issue has still to be definitively demonstrated. Here we describe that FOXP3, induced by CD28 signals in human CD4(+)CD25(-) T lymphocytes, synergizes with RelA on a regulatory region of Cd25 promoter to mediate the transcriptional activation of Cd25 gene. We found that a striking feature of this regulatory region is the presence of a κB site and of two tandem copies of a non-consensus FOXP3 binding site separated at 5' ends by 19 nucleotides that allow FOXP3 and RelA binding to DNA and their physical interaction. The occupancy of the two FOXP3 binding sites in conjunction with RelA binding site occupancy allows FOXP3 to function as a positive activator of Cd25 gene. Indeed mutations of both FOXP3 binding sites such as mutation of κB site on Cd25 promoter abolished FOXP3 activatory functions. Moreover, FOXP3 mutation ΔE251, that compromises FOXP3 homotypic interactions, failed to trans activate Cd25 promoter, suggesting that both FOXP3 DNA binding and dimerization are required to trans activate Cd25 promoter. These findings identify a novel mechanism by which RelA and FOXP3 cooperate to mediate transcriptional regulation of target genes and characterize a region on Cd25 promoter where FOXP3 dimer could bridge intramolecularly two DNA sites and trans activate Cd25 gene.
authors.affiliation: Department of Biology and Biotechnology Charles Darwin, University Sapienza of Rome, Rome, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Camperio
authors.forename: Silvana
authors.initials: S
authors.lastname: Caristi
authors.forename: Giorgia
authors.initials: G
authors.lastname: Fanelli
authors.forename: Marzia
authors.initials: M
authors.lastname: Soligo
authors.forename: Paola
authors.initials: P
authors.lastname: Del Porto
authors.forename: Enza
authors.initials: E
authors.lastname: Piccolella
mesh_terms: D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D018106:CD28 Antigens / Q000378:metabolism; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism; D002478:Cells, Cultured; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D006801:Humans; D015151:Immunoblotting; D053645:Interleukin-2 Receptor alpha Subunit / Q000235:genetics / Q000378:metabolism*; D019169:Jurkat Cells; D008213:Lymphocyte Activation; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051996:Transcription Factor RelA / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D015854:Up-Regulation
chemical_list: D018106:CD28 Antigens; C418974:FOXP3 protein, human; D051858:Forkhead Transcription Factors; D053645:Interleukin-2 Receptor alpha Subunit; C498143:RELA protein, human; D051996:Transcription Factor RelA