Tsix transcription- versus RNA-based mechanisms in Xist repression and epigenetic choice.
Tsix transcription- versus RNA-based mechanisms in Xist repression and epigenetic choice.
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Xist 抑制和表观遗传选择中的 Tsix 转录机制与基于 RNA 的机制。
DOI：
10.1016/j.cub.2004.09.053
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
Lee,JeannieT
中科院分区：
文献类型：
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作者：
Shibata,Shinwa;Lee,JeannieT
最近的调查已经揭示了惊人的数量（>2500）的天然存在的反义转录本[1-4]，但它们的功能仍然在很大程度上未被发现。显然需要更好地理解反义机制，因为它们在基因调控和疾病中可能具有不同的作用[5-8]。X失活是一个有据可查的案例，X连锁基因表达在XX女性和XY男性之间均衡的机制[9]。反义基因Tsix [6]决定X染色体选择并抑制非编码沉默物Xist[10-12]。原则上，Tsixaction可能涉及RNA，转录行为或局部染色质。在这里，我们创造了新的Tsix等位基因来区分转录与RNA为基础的机制。当Tsix转录在Xist之前终止（TsixTRAP）时，Tsix不能阻断Xist的调节，这表明重叠反义转录的重要性。为了将转录行为与RNA分离，我们以反向敲入TsixcDNA（TsixcDNA）以恢复RNA水平，而不进行跨Xist的同时转录。然而，TsixcDNA不能补充TsixTRAP。令人惊讶的是，这两个突变都破坏了选择，表明这一表观遗传步骤需要转录。我们的结论是，加工的反义RNA并不单独作用，而Tsix的功能特别需要通过Xist进行反平行转录。提出了一种基于转录的反馈调节机制。
Recent inquiries have revealed a surprisingly large number (>2500) of naturally occurring antisense transcripts [1–4], but their function remains largely undiscovered. A better understanding of antisense mechanisms is clearly needed because of their potentially diverse roles in gene regulation and disease [5–8]. A well-documented case occurs in X inactivation, the mechanism by which X-linked gene expression is equalized between XX females and XY males [9]. The antisense geneTsix[6] determines X chromosome choice and represses the noncoding silencer,Xist[10–12]. In principle,Tsixaction may involve RNA, the act of transcription, or local chromatin. Here, we create novelTsixalleles to distinguish transcription- versus RNA-based mechanisms. WhenTsixtranscription is terminated beforeXist(TsixTRAP),Tsixcannot blockXistupregulation, suggesting the importance of overlapping antisense transcription. To separate the act of transcription from RNA, we knocked inTsixcDNA in the reverse orientation (TsixcDNA) to restore RNA levels inciswithout concurrent transcription acrossXist. However,TsixcDNAcannot complementTsixTRAP. Surprisingly, both mutations disrupt choice, indicating that this epigenetic step requires transcription. We conclude that the processed antisense RNA does not act alone and thatTsixfunction specifically requires antiparallel transcription throughXist. A mechanism of transcription-based feedback regulation is proposed.