Mi. Fujii et al., Activation of oncogenic transcription factor AP-1 in T cells infected withhuman T cell leukemia virus type 1, AIDS RES H, 16(16), 2000, pp. 1603-1606
Human T cell leukemia virus type 1 (HTLV-1) Tax protein transforms primary
human T cells in vitro. We previously showed that Tax induces the expressio
n of various family members of the transcription factor AP-1 such as c-Jun,
JunD, c-Fos, and Fra-1 at the mRNA level in T cells. In this study, we hav
e examined the ability of Tax to activate transcription through the AP-1-bi
nding site (AP-1 site). A transient transfection study showed that Tax can
activate transcription through the AP-1-binding site in a human T cell line
, whereas any combination of AP-1 proteins did so much less than Tax, indic
ating that the activation of the AP-1 site by Tax may require a mechanism o
ther than the induction of AP-1 mRNA. Fresh peripheral blood leukemia cells
of all surveyed ATL patients displayed constitutive AP-1 DNA-binding activ
ity, whereas no normal individuals did. However, the NTLV-1 genes, includin
g tax, are not significantly expressed in fresh leukemia cells from ATL pat
ients. Our present results suggest that activation of AP-1 occurs through T
ax-dependent and -independent mechanisms in HTLV-1-infected T cells, which
may play some roles in dysregulated phenotypes of HTLV-1-infected cells.