MicroRNAs, which are no more than a couple of dozen nucleotides in length, appear to regulate a broad array of physiological and developmental processes. However, their regulatory roles remain largely mysterious, as the functions of only a few of more than 200 known microRNAs have been established. Unlike the large messenger RNA (mRNA) molecules that code for cellular proteins, the tiny microRNAs regulate gene activity by interfering with mRNAs.
According to Golub, while there had been hints that individual miRNAs were switched on or off in cancers, "there hadn't really been a broad view of miRNA profiles in cancer until this work. The first question was, is there anything interesting to find at all? We suspected microRNAs might be involved in cancer because they play important roles in embryonic development."
Golub noted that the small size of microRNAs posed a challenge for using conventional microarray techniques to analyze gene activity. In microarray analysis, vast numbers of DNA genes are attached to a small slide. That slide is then treated with a mixture of fluorescently tagged messenger RNA isolated from cells whose activity is to be analyzed. The RNA molecules attach to their complementary DNA counterparts on the slide. The amount of mRNA, as measured by fluorescence, reflects a gene's activity. However, such mass gene expression profiling is all but impossible with miRNAs because their short sequences are not as distinctive and thus "cross-hybridize" with one another, said Golub.
So, Golub and his colleagues invented a quick, inexpensive, accurate bead-based technique for analyzing miRNA activity. Their technique involves attaching to color-coded plastic beads DNA seque
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Contact: Jim Keeley
keeleyj@hhmi.org
301-215-8858
Howard Hughes Medical Institute
8-Jun-2005