Plant dicer-like proteins: double-stranded RNA-cleaving enzymes for small RNA biogenesis

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• 作者：Akihito Fukudome ; Toshiyuki Fukuhara
• 关键词：DCL ; Dicer ; DsRNA ; binding protein ; MicroRNA ; Small RNA ; Small interfering RNA
• 刊名：Journal of Plant Research
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：130
• 期：1
• 页码：33-44
• 全文大小：
• 刊物类别：Biomedical and Life Sciences
• 刊物主题：Plant Sciences; Plant Ecology; Plant Physiology; Plant Biochemistry;
• 出版者：Springer Japan
• ISSN：1618-0860
• 卷排序：130

文摘

Dicer, a double-stranded RNA (dsRNA)-specific endoribonuclease, plays an essential role in triggering both transcriptional and post-transcriptional gene silencing in eukaryotes by cleaving dsRNAs or single-stranded RNAs bearing stem-loop structures such as microRNA precursor transcripts into 21- to 24-nt small RNAs. Unlike animals, plants have evolved to utilize at least four Dicer-like (DCL) proteins. Extensive genetic studies have revealed that each DCL protein participates in a specific gene silencing pathway, with some redundancy. However, a mechanistic understanding of how the specific action of each DCL protein is regulated in its respective pathway is still in its infancy due to the limited number of biochemical studies on plant DCL proteins. In this review, we summarize and discuss the biochemical properties of plant DCL proteins revealed by studies using highly purified recombinant proteins, crude extracts, and immunoprecipitates. With help from co-factor proteins and an ATPase/DExH-box RNA-helicase domain, the microRNA-producing enzyme DCL1 recognizes bulges and terminal loop structures in its substrate transcripts to ensure accurate and efficient processing. DCL4 prefers long dsRNA substrates and requires the dsRNA-binding protein DRB4 for its activity. The short-dsRNA preference of DCL3 is well suited for short-RNA transcription and subsequent dsRNA formation by coupling between a plant-specific DNA-dependent RNA-polymerase IV and RNA-dependent RNA-polymerase 2 in the transcriptional gene silencing pathway. Inorganic phosphate also seems to play a role in differential regulation of DCL3 and DCL4 activities. Further development of biochemical approaches will be necessary for better understanding of how plant DCL proteins are fine-tuned in each small RNA biogenesis pathway under various physiological conditions.