Mature mammalian T lymphocytes are not postmitotic, but rather can cycle indefinitely between states of rapid cell division and extended quiescence. Each phase of proliferation is apparently triggered by a single polypeptide hormone, interleukin 2 (IL-2). The resting state is associated with the activation of an endogenous endonuclease that introduces nicks in chromatin DNA. Both the specificity of the growth signal and the reversibility of the resting state make this system interesting. During their maturation in the thymus, T-cell precursors are subject to another pattern of growth control. After rapid proliferation, the vast majority arrest their growth, become inert, and die. The mechanisms involved in their death may be unique to immature cells or related to the mechanisms that mediate reversible growth arrest in mature T cells. Our proposal concerns three aspects of growth regulation. One is the molecular basis of IL-2 expression. We will clone the mouse IL-2 genomic DNA and introduce it into lymphoid and nonlymphoid cells to identify sequences necessary for its correct transcription. Another area is the relationship between the normal growth mediator IL-2 and malignant growth. We plan to link an expressible copy of the IL-2 gene to a constitutive promoter and use it to transform cells that are permanently responsive to IL-2, then test these cells for tumorigenicity in vivo. The third and most complex issue is the basis of programmed thymocyte death and its relationship to the mechanism of reversible growth arrest. We will examine interactions between endonucleolytic chromatin nicking, perhaps common to all resting T cells, and the unbalanced nucleotide metabolism and terminal deoxynucleotidyl transferase (TdT) expression that are charcteristic of doomed thymocytes. The cloned TdT gene will be introduced into mature T-cell lines to ask whether TdT activity potentiates DNA damage and/or interacts with drugs that perturb deoxynucleotide pools. The results will test two models for thymocyte death, either linking it to or dissociating it clearly from the growth arrest in mature cells. (HF)

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA039605-02
Application #
3178775
Study Section
Molecular Biology Study Section (MBY)
Project Start
1985-01-01
Project End
1987-12-31
Budget Start
1986-01-01
Budget End
1986-12-31
Support Year
2
Fiscal Year
1986
Total Cost
Indirect Cost
Name
California Institute of Technology
Department
Type
Schools of Arts and Sciences
DUNS #
078731668
City
Pasadena
State
CA
Country
United States
Zip Code
91125
Scherer, L J; Diamond, R A; Rothenberg, E V (1994) Developmental regulation of cAMP signaling pathways in thymocyte development. Thymus 23:231-57
Garrity, P A; Chen, D; Rothenberg, E V et al. (1994) Interleukin-2 transcription is regulated in vivo at the level of coordinated binding of both constitutive and regulated factors. Mol Cell Biol 14:2159-69
Chen, D; Rothenberg, E V (1993) Molecular basis for developmental changes in interleukin-2 gene inducibility. Mol Cell Biol 13:228-37
Rothenberg, E V (1992) The development of functionally responsive T cells. Adv Immunol 51:85-214
Novak, T J; Yoshimura, F K; Rothenberg, E V (1992) In vitro transfection of fresh thymocytes and T cells shows subset-specific expression of viral promoters. Mol Cell Biol 12:1515-27
Rothenberg, E V (1990) Death and transfiguration of cortical thymocytes: a reconsideration. Immunol Today 11:116-9
Novak, T J; Chen, D; Rothenberg, E V (1990) Interleukin-1 synergy with phosphoinositide pathway agonists for induction of interleukin-2 gene expression: molecular basis of costimulation. Mol Cell Biol 10:6325-34
Novak, T J; Rothenberg, E V (1990) cAMP inhibits induction of interleukin 2 but not of interleukin 4 in T cells. Proc Natl Acad Sci U S A 87:9353-7
Novak, T J; White, P M; Rothenberg, E V (1990) Regulatory anatomy of the murine interleukin-2 gene. Nucleic Acids Res 18:4523-33
Rothenberg, E V; Diamond, R A; Pepper, K A et al. (1990) IL-2 gene inducibility in T cells before T cell receptor expression. Changes in signaling pathways and gene expression requirements during intrathymic maturation. J Immunol 144:1614-24

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