Isolation and analysis of a T cell clone variant exhibiting constitutively phosphorylated Ser133 cAMP response element-binding protein

Stanley M. Belkowski, Charles S. Rubin, Michael B. Prystowsky

Research output: Contribution to journalArticle

9 Scopus citations


In driving T cell proliferation, IL-2 stimulates a new program of gene expression that includes proliferating cell nuclear antigen (PCNA), a requisite processivity factor for DNA polymerase δ. PCNA transcription is regulated in part through tandem CRE sequences in the promoter and CRE binding proteins; IL-2 stimulates CREB phosphorylation in the resting cloned T lymphocyte, L2. After culturing L2 cells for greater than 91 days, we consistently isolate a stable variant that exhibits constitutive CREB phosphorylation. L2 and L2 variant cells were tested for IL-2 responsiveness and rapamycin sensitivity with respect to specific kinase activity, PCNA expression and proliferation. In L2 cells, IL-2 stimulated and rapamycin inhibited the following: cAMP-independent CREB kinase activity, PCNA expression and proliferation. In L2 variant cells, CREB kinase activity was constitutively high; IL-2 stimulated and rapamycin blocked PCNA expression and proliferation. These results indicate that IL-2 induces a rapamycin- sensitive, cAMP-independent CREB kinase activity in L2 cells. However, phosphorylation of CREB alone is not sufficient to drive PCNA expression and L2 cell proliferation in the absence of IL-2.

Original languageEnglish (US)
Pages (from-to)659-665
Number of pages7
JournalJournal of Immunology
Issue number2
Publication statusPublished - Jul 15 1998


ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology

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