Identification and characterization of a constitutively active STAT5 mutant that promotes cell proliferation
Identification and characterization of a constitutively active STAT5 mutant that promotes cell proliferation
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DOI：
10.1128/mcb.18.7.3871
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发表时间：
1998-07-01
影响因子：
5.3
通讯作者：
Kitamura, T
中科院分区：
文献类型：
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作者：
Onishi, M;Nosaka, T;Kitamura, T
STAT（信号转导和转录激活因子）蛋白是在细胞因子刺激下酪氨酸残基磷酸化激活的转录因子。STAT家族的7个成员是已知的，包括密切相关的STAT5A和STAT5B，它们可以被各种细胞因子激活。除了乳腺细胞中催乳素依赖性β -酪蛋白的产生外，STAT5在各种系统中激活的生物学后果尚不清楚。我们应用pcr驱动的随机突变和逆转录病毒介导的表达筛选系统来鉴定STAT5的组成活性形式。通过这种策略，我们已经确定了一个具有两个氨基酸取代的组成活性STAT5突变体；一个位于假定的DNA结合域（H299R）的上游，另一个位于转激活域（S711F）。突变体STAT5在酪氨酸残基上被组成性磷酸化，定位于细胞核，并具有转录活性。突变体STAT5的表达部分缺失了白细胞介素3 （IL-3）作为IL-3依赖性细胞系的生长刺激剂。对突变体STAT5的进一步分析表明，这两个突变都是核定位、有效转录激活和诱导il -3依赖性细胞系Ba/F3不依赖il -3生长所必需的，并且表明组成性激活的分子基础是突变体STAT5磷酸化形式的稳定性。
STAT (signal transducers and activators of transcription) proteins are transcription factors which are activated by phosphorylation on tyrosine residues upon stimulation by cytokines. Seven members of the STAT family are known, including the closely related STAT5A and STAT5B, which are activated by various cytokines. Except for prolactin-dependent beta-casein production in mammary gland cells, the biological consequences of STAT5 activation in various systems are not clear. We applied PCR-driven random mutagenesis and a retrovirus-mediated expression screening system to identify constitutively active forms of STAT5. By this strategy, we have identified a constitutively active STAT5 mutant which has two amino acid substitutions; one is located upstream of the putative DNA binding domain (H299R), and the other is located in the transactivation domain (S711F). The mutant STAT5 was constitutively phosphorylated on tyrosine residues, localized in the nucleus, and was transcriptionally active. Expression of the mutant STAT5 partially dispenses with interleukin 3 (IL-3) as a growth stimulant of IL-3-dependent cell lines. Further analyses of the mutant STAT5 have demonstrated that both of the mutations are required for nuclear localization, efficient transcriptional activation, and induction of IL-3-independent growth of an IL-3-dependent cell line, Ba/F3, and have indicated that a molecular basis for the constitutive activation is the stability of the phosphorylated form of the mutant STAT5.