Dicer proteins are known to produce small RNAs (sRNAs) from long double-stranded RNA (dsRNA) templates. These sRNAs are bound by Argonaute proteins, which select the guide strand, often with a 5' end sequence bias. However, Dicer proteins have never been shown to have sequence cleavage preferences. In Paramecium development, two classes of sRNAs that are required for DNA elimination are produced by three Dicer-like enzymes: Dcl2, Dcl3, and Dcl5. Through in vitro cleavage assays, we demonstrate that Dcl2 has a strict size preference for 25 nt and a sequence preference for 5' U and 5' AGA, while Dcl3 has a sequence preference for 5' UNG. Dcl5, however, has cleavage preferences for 5' UAG and 3' CUAC/UN, which leads to the production of RNAs precisely matching short excised DNA elements with corresponding end base preferences. Thus, we characterize three Dicer-like enzymes that are involved in Paramecium development and propose a biological role for their sequence-biased cleavage products.

中文翻译：

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具有序列切割偏好的 Dicer 样酶。

已知 Dicer 蛋白可从长双链 RNA (dsRNA) 模板产生小 RNA (sRNA)。这些 sRNA 与 Argonaute 蛋白结合，后者选择引导链，通常具有 5' 末端序列偏差。然而，Dicer 蛋白从未被证明具有序列切割偏好。在草履虫发育过程中，消除 DNA 所需的两类 sRNA 由三种 Dicer 样酶产生：Dcl2、Dcl3 和 Dcl5。通过体外切割试验，我们证明 Dcl2 对 25 nt 有严格的大小偏好，对 5' U 和 5' AGA 有序列偏好，而 Dcl3 对 5' UNG 有序列偏好。然而，Dcl5 对 5' UAG 和 3' CUAC/UN 具有切割偏好，这导致 RNA 的产生与相应的末端碱基偏好精确匹配的短切除 DNA 元件。