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Complex cell cycle abnormalities caused by human T-lymphotropic virus type 1 Tax.
Liangpeng Yang1, Naoe Kotomura, Yik-Khuan Ho
1Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Rd., Bethesda, MD 20814, USA.
The Human T-lymphotropic virus type 1 (HTLV-1) trans-activator Tax induces cellular senescence, not proliferation, by upregulating p21 and p27. A small cell variant population bypasses this senescence.
Area of Science:
- Virology
- Cell Biology
- Oncology
Background:
- Human T-lymphotropic virus type 1 (HTLV-1) causes adult T-cell leukemia/lymphoma (ATL).
- The viral trans-activator Tax is implicated in ATL's etiology.
- Tax upregulates p27(Kip1) and p21(CIP1/WAF1), leading to cellular senescence.
Purpose of the Study:
- To investigate the effect of Tax on cell cycle progression using reporter cell lines.
- To challenge the notion that HTLV-1 infection promotes cell proliferation.
Main Methods:
- Utilized time-lapse microscopy.
- Employed HeLa/18x21-EGFP and HeLa-FUCCI reporter cell lines.
- Analyzed Tax-expressing cells and nocodazole-treated cells.
Main Results:
- Tax-expressing HeLa cells showed elongated or stalled cell cycle phases.
- Many cells bypassed mitosis, becoming senescent with enlarged nuclei and cellular content.
- A small variant population with high Tax expression progressed through mitosis normally.
Conclusions:
- HTLV-1 Tax induces cell cycle arrest and senescence, contradicting proliferation theories.
- Spontaneous genetic or epigenetic changes can allow Tax-expressing cells to evade senescence.
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