Two Cap-Binding Proteins CBP20 and CBP80 are Involved in Processing Primary MicroRNAs
Two Cap-Binding Proteins CBP20 and CBP80 are Involved in Processing Primary MicroRNAs
复制标题
DOI：
10.1093/pcp/pcn146
复制
发表时间：
2008-11-01
影响因子：
4.9
通讯作者：
Chua, Nam-Hai
中科院分区：
文献类型：
--
作者：
Kim, Sanghee;Yang, Jun-Yi;Chua, Nam-Hai
MicroRNA（miRNAs）是一类长度为21 nt的RNA，通过介导靶转录物的翻译抑制或切割来调控植物体内的许多生物学过程。拟南芥突变体的miRNA生物合成缺陷具有重叠和高度多效性的表型，包括锯齿叶和阿坝过敏。最近的证据表明，miRNA基因由RNA聚合酶II（Pol II）转录。由于Pol II转录物是加帽的，我们假设CBP（帽结合蛋白）20和80可能与加帽的初级miRNA（pri-miRNA）转录物结合，并在其加工中发挥作用。在这里，我们发现cbp 20和cbp 80突变体具有降低的miRNA水平和增加的pri-miRNA水平。免疫共沉淀实验显示pri-miRNAs 159、166、168和172可以与CBP 20和CBP 80相关联。我们发现，CBP 20和CBP 80是稳定的阿坝通过翻译后机制，这些蛋白质是必需的阿坝诱导miR 159在种子萌发过程中。ABA处理的cbp 20/80突变体种子中miR 159积累的缺乏导致MYB 33和MYB 101转录物水平增加，并且推测这些正调节物的更高水平导致阿坝超敏性。遗传和分子分析表明，CBP 20和80在与SE和HYL 1相同的发育途径中具有重叠功能。我们的研究结果确定了miRNA生物合成中的新组分。
MicroRNAs (miRNAs) are 21 nt RNAs that regulate many biological processes in plants by mediating translational inhibition or cleavage of target transcripts. Arabidopsis mutants defective in miRNA biogenesis have overlapping and highly pleiotropic phenotypes including serrated leaves and ABA hypersensitivity. Recent evidence indicates that miRNA genes are transcribed by RNA polymerase II (Pol II). Since Pol II transcripts are capped, we hypothesized that CBP (cap-binding protein) 20 and 80 may bind to capped primary miRNA (pri-miRNA) transcripts and play a role in their processing. Here, we show that cbp20 and cbp80 mutants have reduced miRNA levels and increased pri-miRNA levels. Co-immunoprecipitation experiments revealed that pri-miRNAs 159, 166, 168 and 172 could be associated with CBP20 and CBP80. We found that CBP20 and CBP80 are stabilized by ABA by a post-translational mechanism, and these proteins are needed for ABA induction of miR159 during seed germination. The lack of miR159 accumulation in ABA-treated seeds of cbp20/80 mutants leads to increased MYB33 and MYB101 transcript levels, and presumably higher levels of these positive regulators result in ABA hypersensitivity. Genetic and molecular analyses show that CBP20 and 80 have overlapping function in the same developmental pathway as SE and HYL1. Our results identify new components in miRNA biogenesis.