The trans-activator tax of human T-cell leukemia virus type 1 (HTLV-1) interacts with cAMP-responsive element (CRE) binding and CRE modulator proteins that bind to the 21-base-pair enhancer of HTLV-1.
The trans-activator protein Tax of human T-cell leukemia virus type 1 (HTLV-1) activates the viral 21-base-pair (bp) enhancer in the long terminal repeat and has been suggested to associate indirectly with the enhancer DNA. To demonstrate this, we used DNA-affinity precipitation assay and detected the Tax protein in 21-bp DNA-protein complexes isolated from HTLV-1-infected cells. To identify cellular components in the complexes, we tested various 21-bp DNA-binding proteins by gel electrophoretic mobility-shift assay. Each binding protein gave a shifted band of each 21-bp DNA-protein complex, and exogenously added Tax protein further shifted these bands of cAMP-responsive element (CRE) binding protein (CREB) and CRE modulator but did not shift other bands. Anti-Tax antibodies blocked formation of the complex, indicating complex formations of [Tax-CREB(or CRE modulator)-21-bp DNA]. The formations of these complexes paralleled the functional activities of Tax mutants. Furthermore, the Tax-CREB complex was detected in a nuclear extract of HTLV-1-infected cells, and the Tax-CREB-21-bp-DNA complex was demonstrated as a major component of Tax complexes containing the 21-bp DNA probe. These observations indicate that Tax protein binds to CREB and CRE modulator and the complexes then bind to the 21-bp enhancer, suggesting that the complex binding to the enhancer mediates trans-activation of transcription.
Suzuki
T
T
Department of Cellular and Molecular Biology, University of Tokyo, Japan.
Fujisawa
J I
JI
Toita
M
M
Yoshida
M
M
D002467:Cell Nucleus / Q000737:chemistry; D051786:Cyclic AMP Response Element Modulator; D004279:DNA, Viral / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004742:Enhancer Elements, Genetic / Q000235:genetics; D015967:Gene Expression Regulation, Viral; D016356:Gene Products, tax / Q000378:metabolism*; D006639:Histidine; D015368:Human T-lymphotropic virus 1 / Q000235:genetics*; D009698:Nucleoproteins / Q000378:metabolism; D011993:Recombinant Fusion Proteins; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid; D012097:Repressor Proteins; D015533:Transcriptional Activation
D004279:DNA, Viral; D004268:DNA-Binding Proteins; D016356:Gene Products, tax; D009698:Nucleoproteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D051786:Cyclic AMP Response Element Modulator; D006639:Histidine