Human T-cell leukemia virus type 2 Tax protein induces interleukin 2-independent growth in a T-cell line.
BACKGROUND
While human T-cell leukemia virus type 1 (HTLV-1) is a causative agent of adult T-cell leukemia, HTLV type 2 (HTLV-2) is not associated with this malignancy. Accumulating evidence suggests that Tax, a transforming protein of HTLV-1 or HTLV-2, plays a crucial role in the distinctive pathogenesis of these two infections. We herein examined whether Tax2 by itself has a growth promoting activity in a mouse T-cell line CTLL-2, and compared the activity with that of Tax1.


RESULTS
We found that Tax2 converts the cell growth of CTLL-2 from an interleukin(IL)-2-dependent growth into an independent one. Cyclosporine A, an inhibitor of transcription factor NFAT, inhibited the growth of two out of four Tax2-transformed CTLL-2 cells, but it had little effect on two Tax1-transformed cells. While the HTLV-2-transformed human T-cell lines produce a significant amount of IL-2, Tax2-transformed CTLL-2 cells only produced a minimal amount of IL-2. These results thus suggest that NFAT-inducible gene(s) other than IL-2 play a role in the cell growth of Tax2-transformed CTLL-2 cells.


CONCLUSIONS
These results show that HTLV-2 Tax2 by itself has a growth promoting activity toward a T-cell line CTLL-2, and the CTLL-2 assay used in this study may therefore be a useful tool for comparing the activity of Tax2 with that of Tax1 in T-cells, thereby elucidating the mechanism of HTLV-1 specific leukemogenesis.
Kondo
Rie
R
Division of Virology, Niigata University Graduate School of Medical and Dental Sciences, 1-757 Asahimachi-Dori, Niigata 951-8510, Japan. rierie-j@d6.dion.ne.jp
Higuchi
Masaya
M
Takahashi
Masahiko
M
Oie
Masayasu
M
Tanaka
Yuetsu
Y
Gejyo
Fumitake
F
Fujii
Masahiro
M
D000818:Animals; D002460:Cell Line; D002461:Cell Line, Transformed; D049109:Cell Proliferation; D002472:Cell Transformation, Viral; D016356:Gene Products, tax / Q000502:physiology*; D015367:Human T-lymphotropic virus 2 / Q000472:pathogenicity / Q000502:physiology*; D006801:Humans; D007376:Interleukin-2 / Q000378:metabolism*; D051379:Mice; D013601:T-Lymphocytes / Q000166:cytology* / Q000821:virology*
D016356:Gene Products, tax; D007376:Interleukin-2