Chen, Dan and Rothenberg, Ellen V. (1993) Molecular basis for developmental changes in interleukin-2 gene inducibility. Molecular and Cellular Biology, 13 (1). pp. 228-237. ISSN 0270-7306 http://resolver.caltech.edu/CaltechAUTHORS:CHEmcb93
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At least three stages in the intrathymic development of pre-T cells are demarcated by differences in the competence to express the interleukin-2 (IL-2) gene as an acute response to stimulation. IL-2 inducibility appears to be acquired relatively early, prior to T-cell receptor (TcR) gene rearrangement. It is then abrogated during the stage when cells are subject to positive and negative selection, i.e., the fate determination processes that select cells for maturation or death. IL-2 inducibility finally reappears in mature classes of thymocytes that have undergone positive selection. To provide a basis for a molecular explanation of these developmental transitions, we have examined the representation in different thymocyte subsets of a set of DNA-binding proteins implicated in IL-2 gene regulation. As the DNA-binding activities of many factors are elicited only by inductive stimuli, the cells were cultured in the presence or absence of the calcium ionophore A23187 and phorbol ester. Our results separate these factors into four regulatory classes: (i) constitutive factors, such as Oct-1 and probably Sp1, that are expressed in thymocytes at all stages; (ii) inducible factors, such as NF-kappa B and complexes binding to the region of a CD28 response element, that can be activated in all thymocytes, including those cells (CD4+ CD8+ TcRlow) that can undergo selection; (iii) inducible factors, such as NF-AT and AP-1, that can be activated in mature (CD4+ CD8- TcRhigh) and immature (CD4- CD8- TcR-) thymocytes alike but not in the transitional stages when the cells (CD4+ CD8+ TcRlow) are subject to selection; and (iv) a factor containing CREB, which can be activated in thymocytes of all developmental stages by culture but does not require specific induction. These results verify that inducible transcription factors are targets of intrathymic developmental change. They also identify NF-AT and AP-1 as factors that are particularly sensitive to the mechanism altering thymocyte responses during the stages when thymocytes may undergo positive and negative selection.
|Additional Information:||Copyright © 1993 by the American Society for Microbiology. Received 8 July 1992/Returned for modification 13 August 1992/Accepted 5 October 1992 We are particularly indebted to Mark Montminy and Rodrigo Bravo, who kindly provided valuable antibodies. We also thank Jerry Crabtree and Frank Calzone for helpful technical advice, Rochelle Diamond for continuing guidance and help with cell separation and analysis, Steven Shen for expert maintenance of the SCID mouse colony, Patrick Koen for key assistance with flow cytometry; and Peter Dervan for generously making the Phosphor-Imager available to us. We thank Eric Davidson for critical reading and thoughtful comments on the manuscript. Expert help in the preparation of the manuscript was provided by Cathy Blagg, and Robert Turring gave valuable assistance with the figures. This research was supported by a seed grant from The Lucille P. Markey Charitable Trust program in developmental biology and subsequently by PHS grants AI19752 and CA39605. Dan Chen acknowledges a fellowship from the Gordon Ross Foundation. The Caltech Flow Cytometry/Cell Sorting Facility and Biopolymer Synthesis Facility were supported in part by NCI Cancer Center core grant CA32911 and in part by funds from The Markey Charitable Trust.|
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