A transcription function for the T cell-specific adapter (TSAd) protein in T cells: critical role of the TSAd Src homology 2 domain.
T cell-specific adapter (TSAd) protein is an Src homology 2 (SH2) domain-containing adapter molecule implicated in T cell receptor for antigen (TCR)-mediated interleukin 2 (IL-2) secretion in T cells. Here, we demonstrate that a substantial fraction of TSAd is found in the T cell nucleus. Nuclear import of TSAd is an active process that depends on TSAd SH2 domain recognition of a phosphotyrosine-containing ligand. Importantly, we show that TSAd can act as a potent transcriptional activator in T cells. Furthermore, the TSAd SH2 domain appears to be essential for this transcription-activating function independent of its role in nuclear import. Biochemical analyses suggest that a single TSAd SH2 domain ligand of 95-100 kD may be involved in these processes. Consistent with a role as a transcription activator, cotransfection of TSAd with an IL-2 promoter-reporter gene construct results in a considerable upregulation of IL-2 promoter activity. Further, we show that this augmentation requires a functional TSAd SH2 domain. However, TSAd does not appear to modulate the activity of the major recognized IL-2 gene transcription factors, nuclear factor kappaB (NF-kappaB), nuclear factor of activated T cells (NFAT), or activator protein 1 (AP-1). These findings point to the function of TSAd as a novel transcription-regulatory protein in T cells and illustrate the importance of the TSAd SH2 domain in this role.
Marti
F
F
T Cell Signaling Laboratory, Hospital for Special Surgery, Weill Medical College and Graduate School of Medical Sciences of Cornell University, New York, New York 10021, USA.
Post
N H
NH
Chan
E
E
King
P D
PD
D021581:Active Transport, Cell Nucleus; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D019556:COS Cells; D002352:Carrier Proteins / Q000737:chemistry* / Q000502:physiology*; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D017930:Genes, Reporter; D006801:Humans; D007376:Interleukin-2 / Q000235:genetics; D019169:Jurkat Cells; D011401:Promoter Regions, Genetic; D013601:T-Lymphocytes / Q000276:immunology*; D014157:Transcription Factors / Q000737:chemistry / Q000502:physiology; D015533:Transcriptional Activation; D018909:src Homology Domains
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D007376:Interleukin-2; C405691:SH2D2A protein, human; D014157:Transcription Factors