Functional Disruption of the CD28 Gene Transcriptional Initiator in Senescent T Cells

Abbe N. Vallejo, Cornelia M. Weyand, Jörg J. Goronzy

Research output: Contribution to journalArticlepeer-review

57 Scopus citations


We recently reported that aging is accompanied by the emergence of CD4 +CD28null T cells, a functionally aberrant lymphocyte subset rarely seen in individuals younger than 40 years. Here, we directly examined whether the lack of CD28 expression is due to a defect at the level of transcriptional initiation. Molecular studies reveal that CD28 gene transcription is controlled by two sequence motifs, sites α and β. In vitro transcription assays using initiator-dependent DNA templates revealed that reversed polarity or the deletion of either motif inhibited transcription, indicating that α/β sequences constitute a composite initiator. Moreover, nuclear extracts from CD28null cells failed to activate transcription of αβ-initiator DNA templates. Transcription of such templates was, however, restored with the addition of extracts from CD28 + cells. Although previously described initiator elements have been defined by a consensus sequence, the αβ-initiator has no homology to such sequence. These studies demonstrate that initiators have functions other than positioning elements for the basal transcription complex. Rather, initiators can have a direct role in regulating the expression of specific genes. The gain or loss of initiator activity can be an important determinant of cell phenotypes.

Original languageEnglish (US)
Pages (from-to)2565-2570
Number of pages6
JournalJournal of Biological Chemistry
Issue number4
StatePublished - Jan 26 2001

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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