Most microRNAs (miRNAs) are processed by two ribonuclease III enzymes. The first cleavage is performed by Microprocessor that is composed of RNase III enzyme Drosha and DGCR8, and the second by another RNase III enzyme Dicer. There are many examples of miRNAs that are poor substrates for Drosha and Dicer, owing to their suboptimal structures. However, a number of these suboptimal miRNAs are known to be expressed at the same or higher level as their neighboring structurally-optimal miRNAs. Recent studies suggest that the clustered orientation of these suboptimal miRNAs is the explanation for this phenomenon. It has been observed that the biogenesis of these suboptimal miRNAs can be affected by the expression of their neighboring optimal miRNAs. This principle is expected to apply more broadly, as it has been shown that a large percentage of suboptimal miRNAs reside within operons.

中文翻译：

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MicroRNA 聚类对次优 microRNA 生物发生的影响

大多数微 RNA (miRNA) 由两种核糖核酸酶 III 酶处理。第一次切割由微处理器执行，微处理器由 RNase III 酶 Drosha 和 DGCR8 组成，第二次切割由另一种 RNase III 酶 Dicer 执行。由于其次优结构，有许多 miRNA 是 Drosha 和 Dicer 的不良底物的例子。然而，已知许多这些次优 miRNA 的表达水平与其相邻的结构优化 miRNA 相同或更高。最近的研究表明，这些次优 miRNA 的聚集方向是对这种现象的解释。已经观察到，这些次优 miRNA 的生物发生会受到其邻近最优 miRNA 表达的影响。预计这一原则将更广泛地适用，