Long noncoding RNAs (lncRNAs) are emerging as potential key regulators in gene expression networks and exhibit a surprising range of shapes and sizes. Several distinct classes of lncRNAs are transcribed from different DNA elements, including promoters, enhancers, and intergenic regions in eukaryotic genomes. Additionally, others are derived from long primary transcripts with noncanonical RNA processing pathways, generating new RNA species with unexpected formats. These lncRNAs can be processed by several mechanisms, including ribonuclease P (RNase P) cleavage to generate mature 3′ ends, capping by small nucleolar RNA (snoRNA)–protein (snoRNP) complexes at their ends, or the formation of circular structures. Here we review current knowledge on lncRNAs and highlight the most recent discoveries of the underlying mechanisms related to their formation.

长的非编码RNA（lncRNA）逐渐成为基因表达网络中潜在的关键调控因子，并呈现出令人惊讶的形状和大小范围。从不同的DNA元件转录出几类不同的lncRNA，包括真核生物基因组中的启动子，增强子和基因间区域。此外，其他衍生自具有非规范RNA处理途径的长一级转录本，从而产生了具有意外格式的新RNA种类。这些lncRNA可以通过多种机制进行加工，包括核糖核酸酶P（RNase P）裂解以生成成熟的3'末端，末端被小核仁RNA（snoRNA）-蛋白质（snoRNP）复合物封端或形成环状结构。 在这里，我们审查有关lncRNAs的当前知识，并强调与它们的形成有关的潜在机制的最新发现。