The frequency natural antisense transcript first promotes, then represses, frequency gene expression via facultative heterochromatin
The frequency natural antisense transcript first promotes, then represses, frequency gene expression via facultative heterochromatin
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DOI：
10.1073/pnas.1406130112
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发表时间：
2015-04-07
影响因子：
11.1
通讯作者：
Belden, William J.
中科院分区：
文献类型：
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作者：
Li, Na;Joska, Tammy M.;Belden, William J.
生物钟由一个相互连接的反馈环网络控制，需要组蛋白修饰和染色质重塑。长非编码天然反义转录本(NAT)起源于哺乳动物的周期和脉孢子虫的频率(FRQ)。为了了解NAT在时钟中的作用，我们将FRQ反义转录本QRF(FRQ反向拼写)置于可诱导启动子的控制下。替换内源QRF启动子改变了FRQ异染色质的形成和DNA甲基化。此外，结构性的、低水平的QRF诱导对内源节律和昼夜节律输出产生了显著的影响。令人惊讶的是，尽管异染色质沉默需要QRF，但QRF的诱导最初通过创造一个更允许的局部染色质环境来促进FRQ基因的表达。在Delta VVD株中，当潮霉素抗性基因的NAT从内源VVD启动子上被赶走时，也观察到反义表达在沉默前通过在收敛位点形成异染色质而最初促进正义基因的表达。FRQ的兼性异染色质沉默的功能与先前描述的VVD依赖的沉默是平行的，是建立适当的昼夜节律所必需的。因此，通过不依赖于Dicer的siRNA介导的兼性异染色质进行的抑制在很大程度上独立于其他反馈过程，并伴随着其他反馈过程发生。
The circadian clock is controlled by a network of interconnected feedback loops that require histone modifications and chromatin remodeling. Long noncoding natural antisense transcripts (NATs) originate from Period in mammals and frequency (frq) in Neurospora. To understand the role of NATs in the clock, we put the frq antisense transcript qrf (frq spelled backwards) under the control of an inducible promoter. Replacing the endogenous qrf promoter altered heterochromatin formation and DNA methylation at frq. In addition, constitutive, low-level induction of qrf caused a dramatic effect on the endogenous rhythm and elevated circadian output. Surprisingly, even though qrf is needed for heterochromatic silencing, induction of qrf initially promoted frq gene expression by creating a more permissible local chromatin environment. The observation that antisense expression can initially promote sense gene expression before silencing via heterochromatin formation at convergent loci is also found when a NAT to hygromycin resistance gene is driven off the endogenous vivid (vvd) promoter in the Delta vvd strain. Facultative heterochromatin silencing at frq functions in a parallel pathway to previously characterized VVD-dependent silencing and is needed to establish the appropriate circadian phase. Thus, repression via dicer-independent siRNA-mediated facultative heterochromatin is largely independent of, and occurs alongside, other feedback processes.