Yin Yang 1 is a lipopolysaccharide-inducible activator of the murine 3′ Igh enhancer, hs3
Yin Yang 1 is a lipopolysaccharide-inducible activator of the murine 3′ Igh enhancer, hs3
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DOI：
10.4049/jimmunol.170.11.5549
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发表时间：
2003-06-01
影响因子：
4.4
通讯作者：
Birshtein, BK
中科院分区：
文献类型：
--
作者：
Gordon, SJ;Saeque, S;Birshtein, BK
3' Igh增强子，DNA酶I超敏位点（hs）3B和/或hs 4，是种系所需的。转录，并因此，多个同种型的类别转换重组。已经通过EMSA鉴定了许多hs 3结合转录因子，包括八聚体和NF-κ B家族成员以及Pax 5。我们已经发现，在原代脾B细胞中，转录因子Yin Yang 1（YY 1）与hs 3和内含子增强子Emu的muE 1位点的结合在LPS和其他类别转换重组激活剂的反应中被诱导了类似48小时。在B细胞系中的瞬时转染实验表明YY 1是hs 3的激活剂。有趣的是，YY 1表达水平在静息和LPS刺激的B细胞中没有变化。EMSA混合实验表明，静息B细胞中存在的一种蛋白质阻止YY 1与DNA结合。我们发现，重组视网膜母细胞瘤蛋白（Rb）抑制YY 1的结合，以剂量依赖性的方式，我们已经确定了内源性YY 1与Rb在静息B细胞，但不是在LPS刺激的B细胞的复合物。在静息（GO）B细胞和LPS刺激的B细胞之间也证实了Rb磷酸化状态的差异。这些观察结果表明，在静息B细胞中YY 1与低磷酸化Rb的相互作用阻止YY 1与DNA的相互作用。在类转换激活剂（如LPS）刺激后，Rb变得过度磷酸化，YY 1被释放，然后可以与hs 3增强子和Emu结合。
The 3' Igh enhancers, DNase I hypersensitive site (hs) 3B and/or hs4, are required for germline. transcription, and hence, class' switch recombination for multiple isotypes. A number of hs3-binding transcription factors have, been identified by EMSA, including octamer and NF-kappaB family members, and Pax5. We have found that the binding of the transcription factor, Yin Yang 1 (YY1), to hs3 and to the muE1 site of the intronic enhancer, Emu, is induced in primary splenic B cells after similar to48 h in response LPS and other activators of class switch recombination. Transient transfection experiments in B cell lines indicate that YY1 is an activator of hs3. Interestingly, levels of YY1 expression are unchanged in resting and LPS-stimulated B cells. Mixing experiments followed by EMSA showed that a protein present in resting B cells prevented binding of YY1 to DNA. We found that recombinant retinoblastoma protein (Rb) inhibited binding of YY1 to hs3 in a dose-dependent manner, and we have identified complexes of endogenous YY1 with the Rb in resting B cells, but not in LPS-stimulated B cells. A difference in Rb phosphorylation state was also confirmed between resting (GO) B cells and LPS-stimulated B cells. These observations suggest that the interaction of YY1 with hypophosphorylated Rb in resting B cells prevents interaction of YY1 with DNA. After stimulation with class-switching activators, such as LPS, Rb becomes hyperphosphorylated and YY1 is released and can then bind to the hs3 enhancer and Emu.