Arabidopsis FIERY1, XRN2, and XRN3 are endogenous RNA silencing suppressors
Arabidopsis FIERY1, XRN2, and XRN3 are endogenous RNA silencing suppressors
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DOI：
10.1105/tpc.107.055319
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发表时间：
2007-11-01
期刊：
影响因子：
11.6
通讯作者：
Mallory, Allison C.
中科院分区：
文献类型：
--
作者：
Gy, Isabelle;Gasciolli, Virginie;Mallory, Allison C.
真核防御反应转录后基因沉默（PTGS）由短干扰RNA指导，并通过保守的ARGONAUTE（AGO）蛋白的RNA切割活性阻止入侵核酸。PTGS可以被外源性或内源性抑制因子抵消，包括胞质核糖核酸外切酶XRN 4，其也降解microRNA（miRNA）引导的mRNA切割产物，但在发育中不起明显作用。在这里，我们表明，核外核糖核酸酶XRN 2和XRN 3是内源性PTGS抑制剂。我们还确定了切除的MIRNA环作为XRN 2和XRN 3的模板，并表明XRN 3对正常发育至关重要。独立地，我们确定了核苷酸酶/磷酸酶FIERY 1（FRY 1）作为一个内源性PTGS抑制子通过抑制筛选在亚纯型ago 1遗传背景。FRY 1是酵母Hal 2的六个拟南芥直向同源物之一。酵母hal 2突变体过度积累3 '-磷酸腺苷5'-磷酸，其抑制5 '-> 3'核糖核酸外切酶Xrn 1和Rat 1。fry 1突变体植物概括了xrn突变体的发育和分子特征，并可能通过共同抑制XRN 2，XRN 3和XRN 4来恢复ago 1亚型突变体中的PTGS，从而增加RNA沉默触发因子。我们预计，包含部分受损沉默组分的筛选将揭示使用稳健沉默系统可能无法揭示的额外PTGS抑制子。
The eukaryotic defense response posttranscriptional gene silencing (PTGS) is directed by short-interfering RNAs and thwarts invading nucleic acids via the RNA slicing activity of conserved ARGONAUTE (AGO) proteins. PTGS can be counteracted by exogenous or endogenous suppressors, including the cytoplasmic exoribonuclease XRN4, which also degrades microRNA (miRNA)-guided mRNA cleavage products but does not play an obvious role in development. Here, we show that the nuclear exoribonucleases XRN2 and XRN3 are endogenous PTGS suppressors. We also identify excised MIRNA loops as templates for XRN2 and XRN3 and show that XRN3 is critical for proper development. Independently, we identified the nucleotidase/ phosphatase FIERY1 (FRY1) as an endogenous PTGS suppressor through a suppressor screen in a hypomorphic ago1 genetic background. FRY1 is one of six Arabidopsis thaliana orthologs of yeast Hal2. Yeast hal2 mutants overaccumulate 3'-phosphoadenosine 5'-phosphate, which suppresses the 5'-> 3' exoribonucleases Xrn1 and Rat1. fry1 mutant plants recapitulate developmental and molecular characteristics of xrn mutants and likely restore PTGS in ago1 hypomorphic mutants by corepressing XRN2, XRN3, and XRN4, thus increasing RNA silencing triggers. We anticipate that screens incorporating partially compromised silencing components will uncover additional PTGS suppressors that may not be revealed using robust silencing systems.