A Dicer-Independent Route for Biogenesis of siRNAs that Direct DNA Methylation in Arabidopsis

作者：Ye, Ruiqiang; Chen, Zulong; Lian, Bi; Rowley, M. Jordan; Xia, Ning; Chai, Jijie; Li, Yan; He, Xin-Jian; Wierzbicki, Andrzej T.; Qi, Yijun^*

来源：Molecular Cell, 2016, 61(2): 222-235.

DOI：10.1016/j.molcel.2015.11.015

• RNA-POLYMERASE V
• TRANS-ACTING SIRNAS
• POL IV
• HETEROCHROMATIN FORMATION
• DEPENDENT SIRNAS
• IN-VITRO
• PATHWAY
• GENE
• TRANSCRIPTION
• ARGONAUTE4

DNA methylation directed by 24-nucleotide (nt) small interfering RNAs (siRNAs) plays critical roles in gene regulation and transposon silencing in Arabidopsis. 24-nt siRNAs are known to be processed from double-stranded RNAs by Dicer-like 3 (DCL3) and loaded into the effector Argonaute 4 (AGO4). Here we report a distinct class of siRNAs independent of DCLs (sidRNAs). sidRNAs are present as ladders of similar to 20-60 nt in length, often having the same 50 ends but differing in 3' ends by 1-nt steps. We further show that sidRNAs are associated with AGO4 and capable of directing DNA methylation. Finally we show that sidRNA production depends on distributive 3'-5' exonucleases. Our findings suggest an alternative route for siRNA biogenesis. Precursor transcripts are bound by AGO4 and subsequently subjected to 3'-5' exonucleolytic trimming for maturation. We propose that sidRNAs generated through this route are the initial triggers of de novo DNA methylation.

• 出版日期2016-1-21
• 单位清华大学; 北京生命科学研究所; 北京大学