摘要
Although interdisciplinary research has been heralded as the engine of basic discovery for decades,many in the immunology community have been taken back by the recent marriage between microRNA(miRNA)and immunology.MicroRNAs were first discovered by Ambros and colleagues in 1993.1 They are small untranslated RNAs,highly conserved between different eukaryotic species.2–5 They are encoded by specific genes in the genome,which are controlled at the transcriptional level in a manner similar to protein-encoding genes.2 Following the synthesis of the primary miRNA by RNA polymerase Ⅱ or Ⅲ,nuclear processing by the enzyme Drosha produces a primary miRNA transcript which can be shuttled into the cytoplasm2 Final production of the mature miRNA species requires further cytoplasmic processing by an RNase Ⅲ enzyme called Dicer,producing a 19-to 24-base pair product,capable of being incorporated into the RNA-induced silencing complex.The RNA-induced silencing complex,in turn,is able to use the‘seed sequence’of the miRNA to recognize complementary mRNAtranscripts for degradation or translational silencing.To date,more than 800 human miRNAs have been identified,regulating an estimated 50%of all human genes.Each miRNA appears to regulate the expression of tens to hundreds of genes,thereby functioning as‘master-switches’that regulate and coordinate multiple cellular pathways in important processes such as embryonic development and oncogenesis,as well as cellular growth and proliferation.
