Department of Plant Molecular Biology, University of Lausanne, 1015 Lausanne, Switzerland.
Institute of Biology I, RWTH Aachen University, 52074 Aachen, Germany.
Plant Cell. 2021 May 31;33(4):1381-1397. doi: 10.1093/plcell/koab010.
A large portion of eukaryotic genes are associated with noncoding, natural antisense transcripts (NATs). Despite sharing extensive sequence complementarity with their sense mRNAs, mRNA-NAT pairs elusively often evade dsRNA-cleavage and siRNA-triggered silencing. More surprisingly, some NATs enhance translation of their sense mRNAs by yet unknown mechanism(s). Here, we show that translation enhancement of the rice (Oryza sativa) PHOSPHATE1.2 (PHO1.2) mRNA is enabled by specific structural rearrangements guided by its noncoding antisense RNA (cis-NATpho1.2). Their interaction in vitro revealed no evidence of widespread intermolecular dsRNA formation, but rather specific local changes in nucleotide base pairing, leading to higher flexibility of PHO1.2 mRNA at a key high guanine-cytosine�(GC) regulatory region inhibiting translation, ∼350-nt downstream of the start codon. Sense-antisense RNA interaction increased formation of the 80S complex in PHO1.2, possibly by inducing structural rearrangement within this inhibitory region, thus making this mRNA more accessible to 60S. This work presents a framework for nucleotide resolution studies of functional mRNA-antisense pairs.
真核生物的大部分基因都与非编码的自然反义转录本（NAT）有关。尽管 mRNA-NAT 对与它们的有义 mRNA 具有广泛的序列互补性，但 mRNA-NAT 对通常逃避 dsRNA 切割和 siRNA 触发的沉默。更令人惊讶的是，一些 NAT 通过未知的机制增强其有义 mRNA 的翻译。在这里，我们表明，水稻（Oryza sativa）PHOSPHATE1.2（PHO1.2）mRNA 的翻译增强是由其非编码反义 RNA（顺式-NATpho1.2）指导的特定结构重排所实现的。它们在体外的相互作用没有证据表明广泛的分子间 dsRNA 形成，而是核苷酸碱基配对的特定局部变化，导致起始密码子下游约 350nt 的关键高鸟嘌呤-胞嘧啶（GC）调节区翻译抑制的 PHO1.2 mRNA 更高的灵活性。有义-反义 RNA 相互作用增加了 PHO1.2 中 80S 复合物的形成，可能通过诱导该抑制区的结构重排，从而使该 mRNA 更容易与 60S 结合。这项工作为功能性 mRNA-反义对的核苷酸分辨率研究提供了一个框架。
