Control of IL-2Ralpha gene expression: structural changes within the proximal enhancer/core promoter during T-cell development.
During T-cell development in thymus, CD25, the IL-2 receptor alpha chain (IL-2Ralpha) is already expressed in early double-negative (DN) thymocytes where commitment to T-cell lineage has been established, but subsequently IL-2Ralpha is dramatically down-regulated for the remainder of T-cell development. The loss of IL-2Ralpha expression after expression of the pre-TCR alpha:beta complex on the cell surface is essential for the later specific responses of mature T cells. Using appropriate mouse models and DMS genomic footprinting, we showed that the TATA box in the core promoter region of the murine IL-2Ralpha locus was occupied only in DN CD25+ T cells. Further, by chromatin immunoprecipitation assays, we evidenced that down-regulation of IL-2Ralpha transcription correlated with (i) loss of the basal transcriptional machinery; (ii) dissociation of histone acetylase p300 and BRG1, a member of the ATP-dependent chromatin remodeling complex SWI/SNF; and (iii) histone N-termini dephosphorylation plus deacetylation. In contrast, occupancy of the proximal enhancer region (positive regulatory region I) was not detected by in vivo genomic footprinting though constitutive accessibility of the promoter region for DNase I digestion both in the DN and double-positive stages correlated with the constitutive association of CBP and PCAF to the IL-2Ralpha core promoter. These results exemplify one mechanism by which a promoter enables transcription to switch on and off during T-cell differentiation.
Yeh
Jung-Hua
JH
INSERM U119-IFR57, 27 boulevard Lei Roure, 13009 Marseille, France.
Spicuglia
Salvatore
S
Kumar
Sanjeex
S
Sanchez-Sevilla
Albert
A
Ferrier
Pierre
P
Imbert
Jean
J
D000123:Acetyltransferases / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D002843:Chromatin / Q000378:metabolism; D003850:Deoxyribonuclease I / Q000737:chemistry; D015536:Down-Regulation; D004742:Enhancer Elements, Genetic; D020868:Gene Silencing; D051548:Histone Acetyltransferases; D006657:Histones / Q000378:metabolism; D053645:Interleukin-2 Receptor alpha Subunit; D046911:Macromolecular Substances; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D018123:Receptors, Interleukin / Q000235:genetics*; D020218:Response Elements; D029701:Saccharomyces cerevisiae Proteins; D013601:T-Lymphocytes / Q000276:immunology*; D016385:TATA Box; D013950:Thymus Gland / Q000254:growth & development / Q000276:immunology; D014157:Transcription Factors / Q000378:metabolism
D002843:Chromatin; D006657:Histones; C508018:Il2ra protein, mouse; D053645:Interleukin-2 Receptor alpha Subunit; D046911:Macromolecular Substances; D018123:Receptors, Interleukin; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D000123:Acetyltransferases; D051548:Histone Acetyltransferases; D003850:Deoxyribonuclease I