Hoxb4 transduction down-regulates Geminin protein, providing hematopoietic stem and progenitor cells with proliferation potential
Hoxb4 transduction down-regulates Geminin protein, providing hematopoietic stem and progenitor cells with proliferation potential
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DOI：
10.1073/pnas.1011054107
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发表时间：
2010-11
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通讯作者：
Yoshinori Ohno;S. Yasunaga;M. Ohtsubo;Sayaka Mori;M. Tsumura;S. Okada;T. Ohta;K. Ohtani;Masao Kobayashi;Y. Takihara
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作者：
Yoshinori Ohno;S. Yasunaga;M. Ohtsubo;Sayaka Mori;M. Tsumura;S. Okada;T. Ohta;K. Ohtani;Masao Kobayashi;Y. Takihara
逆转录病毒介导的Hoxb 4的转导增强造血干细胞（HSC）的活性，并且Hoxb 4的强制表达诱导从分化的小鼠胚胎干细胞体外发育为HSCs，但潜在的分子机制仍不清楚。我们以前表明，HSC的活性被废除积累的Geminin，抑制剂的DNA复制许可因子Cdt 1在小鼠Rae 28（也称为Phc 1），它编码的Polycomb组复合物1的成员缺陷。在这项研究中，我们发现Hoxb 4转导减少了Rae 28缺陷小鼠中积累的Geminin，尽管增加了mRNA，并恢复了受损的HSC活性。Geminin的超转导抑制了Hoxb 4转导诱导的HSC活性，而Geminin的敲低促进了克隆形成和再铺板活性，表明Geminin调节在Hoxb 4转导介导的HSC活性增强的分子机制中的重要性。这促进了我们对转导的Hoxb 4如何减少Geminin的研究。我们在体外和体内研究表明，Hoxb 4和Roc 1（也称为Rbx 1）-Ddb 1-Cul 4a泛素连接酶核心组分形成了一个复合物，命名为RDCOXB 4，它作为一个E3泛素连接酶的Geminin和下调Geminin通过泛素-蛋白酶体系统。下调的Geminin和由此产生的E2 F激活可以通过增加加载到染色质上的DNA复制前复合物来为细胞提供增殖潜力。在这里，我们认为，转导Hoxb 4下调Geminin蛋白可能通过构成E3泛素连接酶的Geminin提供造血干细胞和祖细胞的增殖潜力。
Retrovirus-mediated transduction of Hoxb4 enhances hematopoietic stem cell (HSC) activity and enforced expression of Hoxb4 induces in vitro development of HSCs from differentiating mouse embryonic stem cells, but the underlying molecular mechanism remains unclear. We previously showed that the HSC activity was abrogated by accumulated Geminin, an inhibitor for the DNA replication licensing factor Cdt1 in mice deficient in Rae28 (also known as Phc1), which encodes a member of Polycomb-group complex 1. In this study we found that Hoxb4 transduction reduced accumulated Geminin in Rae28-deficient mice, despite increasing the mRNA, and restored the impaired HSC activity. Supertransduction of Geminin suppressed the HSC activity induced by Hoxb4 transduction, whereas knockdown of Geminin promoted the clonogenic and replating activities, indicating the importance of Geminin regulation in the molecular mechanism underlying Hoxb4 transduction-mediated enhancement of the HSC activity. This facilitated our investigation of how transduced Hoxb4 reduced Geminin. We showed in vitro and in vivo that Hoxb4 and the Roc1 (also known as Rbx1)-Ddb1-Cul4a ubiquitin ligase core component formed a complex designated as RDCOXB4, which acted as an E3 ubiquitin ligase for Geminin and down-regulated Geminin through the ubiquitin-proteasome system. Down-regulated Geminin and the resultant E2F activation may provide cells with proliferation potential by increasing a DNA prereplicative complex loaded onto chromatin. Here we suggest that transduced Hoxb4 down-regulates Geminin protein probably by constituting the E3 ubiquitin ligase for Geminin to provide hematopoietic stem and progenitor cells with proliferation potential.