Human microRNAs are processed from capped, polyadenylated transcripts that can also function as mRNAs
Human microRNAs are processed from capped, polyadenylated transcripts that can also function as mRNAs
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DOI：
10.1261/rna.7135204
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发表时间：
2004-12-01
期刊：
影响因子：
4.5
通讯作者：
Cullen, BR
中科院分区：
文献类型：
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作者：
Cai, XZ;Hagedorn, CH;Cullen, BR
microRNA（miRNAs）是一个普遍存在的类似于22-nt非编码调控RNA家族，其表达调控因子至今尚未明确。然而，已知miRNA首先被转录为大部分未结构化的前体，称为初级miRNA（pri-miRNA），其在细胞核中顺序加工，以产生类似于65-nt的pre-miRNA发夹中间体，然后在细胞质中，以产生成熟的miRNA。在这里，我们试图确定负责miRNA转录的RNA聚合酶，并确定全长人类miRNA的结构。我们发现9个人类miRNAs的pri-miRNAs前体都是加帽的和多聚腺苷酸化的，并报告了全长序列，类似于3433-nt pri-miR-21 RNA。该pri-miR-21基因序列的5'侧接能够转录异源mRNA的启动子元件，3'侧接共有聚腺苷酸化序列。发现pri-miRNAs的核加工是有效的，因此在很大程度上阻止了全长pri-miRNAs的核输出。然而，位于蛋白质编码基因的3' UTR中的完整miRNA茎环前体仅适度抑制连接的开放阅读框的表达，这可能是因为3'截短的mRNA仍然可以输出和表达。总之，这些数据表明，人类pri-miRNAs不仅在结构上与mRNAs相似，而且实际上可以同时作为pri-miRNAs和mRNAs发挥功能。
The factors regulating the expression of microRNAs (miRNAs), a ubiquitous family of similar to22-nt noncoding regulatory RNAs, remain undefined. However, it is known that miRNAs are first transcribed as a largely unstructured precursor, termed a primary miRNA (pri-miRNA), which is sequentially processed in the nucleus, to give the similar to65-nt pre-miRNA hairpin intermediate, and then in the cytoplasm, to give the mature miRNA. Here we have sought to identify the RNA polymerase responsible for miRNA transcription and to define the structure of a full-length human miRNA. We show that the pri-miRNA precursors for nine human miRNAs are both capped and polyadenylated and report the sequence of the full-length, similar to3433-nt pri-miR-21 RNA. This pri-miR-21 gene sequence is flanked 5' by a promoter element able to transcribe heterologous mRNAs and 3' by a consensus polyadenylation sequence. Nuclear processing of pri-miRNAs was found to be efficient, thus largely preventing the nuclear export of full-length pri-miRNAs. Nevertheless, an intact miRNA stem-loop precursor located in the 3' UTR of a protein coding gene only moderately inhibited expression of the linked open reading frame, probably because the 3' truncated mRNA could still be exported and expressed. Together, these data show that human pri-miRNAs are not only structurally similar to mRNAs but can, in fact, function both as pri-miRNAs and mRNAs.