Vertebrate segmentation is regulated by the segmentation clock, a biological oscillator that controls periodic formation of somites, or embryonic segments, which give rise to many mesodermal tissue types. This molecular oscillator generates cyclic gene expression with the same periodicity as somite formation in the presomitic mesoderm (PSM), an area of mesenchymal cells that give rise to mature somites. Molecular components of the clock include the Hes/her family of genes that encode transcriptional repressors, but additional genes cycle. Cyclic gene transcripts are cleared rapidly, and clearance depends upon the pnrc2 (proline-rich nuclear receptor co-activator 2) gene that encodes an mRNA decay adaptor. Previously, we showed that the her1 3'UTR confers instability to otherwise stable transcripts in a Pnrc2-dependent manner, however, the molecular mechanism(s) by which cyclic gene transcripts are cleared remained largely unknown. To identify features of the her1 3'UTR that are critical for Pnrc2-mediated decay, we developed an array of transgenic inducible reporter lines carrying different regions of the 3'UTR. We find that the terminal 179 nucleotides (nts) of the her1 3'UTR are necessary and sufficient to confer rapid instability. Additionally, we show that the 3'UTR of another cyclic gene, deltaC (dlc), also confers Pnrc2-dependent instability. Motif analysis reveals that both her1 and dlc 3'UTRs contain terminally-located Pumilio response elements (PREs) and AU-rich elements (AREs), and we show that the PRE and ARE in the last 179 nts of the her1 3'UTR drive rapid turnover of reporter mRNA. Finally, we show that mutation of Pnrc2 residues and domains that are known to facilitate interaction of human PNRC2 with decay factors DCP1A and UPF1 reduce the ability of Pnrc2 to restore normal cyclic gene expression in pnrc2 mutant embryos. Our findings suggest that Pnrc2 interacts with decay machinery components and cooperates with Pumilio (Pum) proteins and ARE-binding proteins to promote rapid turnover of cyclic gene transcripts during somitogenesis.

中文翻译：

---

Pumilio响应和富含AU的元素驱动Pnrc2调节的环状基因转录本的快速衰减。

椎骨分段受分段时钟调节，分段时钟是一种生物振荡器，可控制体节或胚胎节段的周期性形成，从而形成许多中胚层组织类型。该分子振荡器以与早熟中胚层（PSM）中的节体形成相同的周期产生循环基因表达，PSM是间充质细胞的一个区域，会产生成熟的节节。时钟的分子成分包括编码转录阻遏物的Hes / her基因家族，但其他基因却在循环。环状基因转录物可以快速清除，清除取决于编码mRNA衰减衔接子的pnrc2（富含脯氨酸的核受体共激活因子2）基因。之前，我们显示了her1 3'UTR以依赖Pnrc2的方式将不稳定赋予原本稳定的转录本，但是，清除环状基因转录本的分子机制仍然未知。为了鉴定对Pnrc2介导的衰变至关重要的her1 3'UTR的特征，我们开发了一系列携带3'UTR不同区域的转基因诱导型报告基因系。我们发现her1 3'UTR的末端179个核苷酸（nts）是必要且足以赋予快速不稳定性。此外，我们显示另一个环状基因deltaC（dlc）的3'UTR也赋予Pnrc2依赖性不稳定性。母题分析显示，her1和dlc 3'UTR均包含末端定位的Pumilio反应元件（PRE）和富含AU的元件（ARE），并且我们显示了her1 3'UTR驱动器的最后179个nt中的PRE和ARE。报告基因mRNA的快速周转。最后，我们表明，Pnrc2残基和已知可以促进人PNRC2与衰变因子DCP1A和UPF1相互作用的域的突变降低了Pnrc2恢复pnrc2突变体胚胎中正常循环基因表达的能力。我们的发现表明，Pnrc2与衰变机制组件相互作用，并与Pumilio（Pum）蛋白和ARE结合蛋白协同作用，以促进在体发生过程中循环基因转录物的快速更新。