Cell Biology Group, Department of Surgery, University of Maryland School of Medicine, Baltimore, MD 21201 Department of Pathology, University of Maryland School of Medicine, Baltimore, MD 21201 Baltimore Veterans Affairs Medical Center, Baltimore, MD 21201 Laboratory of Genetics, National Institute on Aging-Intramural Research Program, National Institutes of Health, Baltimore, MD 21224.
Mol Biol Cell. 2013 Oct;24(19):3038-46. doi: 10.1091/mbc.E13-05-0287. Epub 2013 Jul 31.
The epithelium of the intestinal mucosa is a rapidly self-renewing tissue in the body, and defects in the renewal process occur commonly in various disorders. microRNAs (miRNAs) posttranscriptionally regulate gene expression and are implicated in many aspects of cellular physiology. Here we investigate the role of miRNA-29b (miR-29b) in the regulation of normal intestinal mucosal growth and further validate its target mRNAs. miRNA expression profiling studies reveal that growth inhibition of the small intestinal mucosa is associated with increased expression of numerous miRNAs, including miR-29b. The simple systemic delivery of locked nucleic acid-modified, anti-miR-29b-reduced endogenous miR-29b levels in the small intestinal mucosa increases cyclin-dependent kinase 2 (CDK2) expression and stimulates mucosal growth. In contrast, overexpression of the miR-29b precursor in intestinal epithelial cells represses CDK2 expression and results in growth arrest in G1 phase. miR-29b represses CDK2 translation through direct interaction with the cdk2 mRNA via its 3'-untranslated region (3'-UTR), whereas point mutation of miR-29b binding site in the cdk2 3'-UTR prevents miR-29b-induced repression of CDK2 translation. These results indicate that miR-29b inhibits intestinal mucosal growth by repressing CDK2 translation.
肠黏膜上皮细胞是体内快速自我更新的组织，在各种疾病中，更新过程的缺陷很常见。微小 RNA（miRNA）在后转录水平上调节基因表达，并与细胞生理的许多方面有关。在这里，我们研究了 miRNA-29b（miR-29b）在调节正常肠黏膜生长中的作用，并进一步验证了其靶 mRNAs。miRNA 表达谱研究表明，小肠黏膜生长抑制与许多 miRNA 的表达增加有关，包括 miR-29b。通过简单的全身递送修饰的锁核酸反义 miR-29b，可减少小肠黏膜中的内源性 miR-29b 水平，从而增加细胞周期蛋白依赖性激酶 2（CDK2）的表达并刺激黏膜生长。相反，在肠上皮细胞中过表达 miR-29b 前体可抑制 CDK2 的表达，并导致 G1 期生长停滞。miR-29b 通过其 3'非翻译区（3'UTR）与 cdk2 mRNA 的直接相互作用来抑制 CDK2 的翻译，而 cdk2 3'UTR 中 miR-29b 结合位点的点突变可防止 miR-29b 诱导的 CDK2 翻译抑制。这些结果表明，miR-29b 通过抑制 CDK2 翻译来抑制肠黏膜生长。
