Ludwig Boltzmann Institute for Cancer Research, Vienna, Austria.
Blood. 2010 Sep 2;116(9):1548-58. doi: 10.1182/blood-2009-12-258913. Epub 2010 May 27.
Stat5 transcription factors are essential gene regulators promoting proliferation, survival, and differentiation of all hematopoietic cell types. Mutations or fusions of oncogenic tyrosine kinases often result in constitutive Stat5 activation. We have modeled persistent Stat5 activity by using an oncogenic Stat5a variant (cS5). To analyze the hitherto unrecognized role of Stat5 serine phosphorylation in this context, we have generated cS5 constructs with mutated C-terminal serines 725 and 779, either alone or in combination. Genetic complementation assays in primary Stat5(null/null) mast cells and Stat5(DeltaN) T cells demonstrated reconstitution of proliferation with these mutants. Similarly, an in vivo reconstitution experiment of transduced Stat5(null/null) fetal liver cells transplanted into irradiated wild-type recipients revealed that these mutants exhibit biologic activity in lineage differentiation. By contrast, the leukemogenic potential of cS5 in bone marrow transplants decreased dramatically in cS5 single-serine mutants or was completely absent upon loss of both serine phosphorylation sites. Our data suggest that Stat5a serine phosphorylation is a prerequisite for cS5-mediated leukemogenesis. Hence, interference with Stat5a serine phosphorylation might provide a new therapeutic option for leukemia and myeloid dysplasias without affecting major functions of Stat5 in normal hematopoiesis.
Stat5 转录因子是促进所有造血细胞类型增殖、存活和分化的重要基因调节剂。致癌酪氨酸激酶的突变或融合常常导致 Stat5 的组成性激活。我们通过使用致癌 Stat5a 变体 (cS5) 来模拟持续的 Stat5 活性。为了分析 Stat5 丝氨酸磷酸化在这种情况下迄今为止尚未被认识到的作用，我们生成了带有突变的 C 末端丝氨酸 725 和 779 的 cS5 构建体，要么单独突变，要么组合突变。在原发性 Stat5(null/null)肥大细胞和 Stat5(DeltaN)T 细胞中的遗传互补测定表明，这些突变体能重建增殖。同样，在转导的 Stat5(null/null)胎肝细胞移植到照射的野生型受体中的体内重建实验表明，这些突变体在线粒体分化中表现出生物活性。相比之下，cS5 在骨髓移植中的致白血病潜力在 cS5 单丝氨酸突变体中显著降低，或者在两个丝氨酸磷酸化位点丢失时完全不存在。我们的数据表明，Stat5a 丝氨酸磷酸化是 cS5 介导的白血病发生的前提条件。因此，干扰 Stat5a 丝氨酸磷酸化可能为白血病和骨髓增生异常提供一种新的治疗选择，而不会影响 Stat5 在正常造血中的主要功能。
