MicroRNA cloning from cells of the immune system

MicroRNAs have emerged as - important posttranscriptional regulators of gene expression. Small RNA cloning is a powerful method to identify new microRNAs (miRNAs) and to profile miRNA expression. In addition, it reveals end heterogeneity that may be important in miRNA function. Here, we describe a protocol that is optimized to clone small RNAs from limited amounts of starting material. This is often the case for studying miRNAs in a highly purified population of immune cells or other primary cell types with limited numbers. The small RNAs cloned with this protocol will have a 5'-PO(4) and 3'-OH group, typical features of miRNAs, so majority of the cloned small RNAs will be miRNAs.