Dimer stability as a determinant of differential DNA binding activity of Stat3 isoforms
Dimer stability as a determinant of differential DNA binding activity of Stat3 isoforms
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DOI：
10.1074/jbc.m005082200
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发表时间：
2000-10-13
影响因子：
4.8
通讯作者：
Schaefer, TS
中科院分区：
文献类型：
--
作者：
Park, OK;Schaefer, LK;Schaefer, TS
Stat3 alpha 和 Stat3 beta 是两种 Stat3 同工型，其 DNA 结合活性存在显着的数量差异。为了检查差异 DNA 结合活性的分子基础，我们测量了 DNA 结合强度和二聚体稳定性，这是造成这些差异的两种可能机制。 Stat3 α 和 Stat3 β 的 DNA 结合强度没有差异，即它们具有相似的 DNA 结合缔合和解离率。然而，使用包括抗磷酸酪氨酸抗体、SH2 结构域蛋白和磷酸肽在内的解离试剂进行的竞争分析表明，Stat3 β 二聚体比 Stat3 α 二聚体更稳定。我们在此报告，激活形式的二聚体稳定性在确定 Stat3 亚型的 DNA 结合活性中起着至关重要的作用。我们发现 Stat3 α 的 C 端缺失增加了 Stat3 α 的 DNA 结合活性和二聚体稳定性。我们的研究结果表明，Stat3 α 的酸性 C 末端区域不会干扰激活的 Stat3 α 二聚体的 DNA 结合，但会破坏 Stat3 α 二聚体形式的稳定性。我们认为体外描述的二聚体稳定性可能是激活的 Stat3 蛋白体内稳定性的潜在机制，调节酪氨酸 705 的去磷酸化。
Stat3 alpha and Stat3 beta are two Stat3 isoforms with marked quantitative differences in their DNA binding activities. To examine the molecular basis of the differential DNA binding activities, we measured DNA binding strength and dimer stability, two possible mechanisms responsible for these differences. Stat3 alpha and Stat3 beta showed no difference in DNA binding strength, i.e. they had similar association and dissociation rates for DNA binding However, competition analyses performed with dissociating reagents including an anti-phosphotyrosine antibody, SH2 domain protein, and a phosphopeptide demonstrated that Stat3 beta dimers are more stable than Stat3 alpha dimers. We report here that dimer stability of activated forms plays a critical role in determining DNA binding activity of Stat3 isoforms. We found that C-terminal deletions of Stat3 alpha increased both DNA binding activity and dimer stability of Stat3 alpha. Our findings suggest that the acidic C-terminal region of Stat3 alpha does not interfere with the DNA binding of activated Stat3 alpha dimers, but destabilizes the dimeric forms of Stat3 alpha. We propose that dimer stability described in vitro may be the underlying mechanism of in vivo stability of activated Stat3 proteins, regulating dephosphorylation of tyrosine 705.