RNA interference : more than a research

In recent years, RNA silencing, usage of small double stranded RNAs of ~21 – 25 base pairs to regulate gene expression, has emerged as a powerful research tool to dissect the role of unknown host cell factors in this 'post-genomic' era. While the molecular mechanism of RNA silencing has not been precisely defined, the revelation that small RNA molecules are equipped with this regulatory function has transformed our thinking on the role of RNA in many facets of biology, illustrating the complexity and the dynamic interplay of cellular regulation. As plants and invertebrates lack the protein-based adaptive immunity that are found in jawed vertebrates, the ability of RNA silencing to shut down gene expression in a sequence-specific manner offers an explanation of how these organisms counteract pathogen invasions into host cells. It has been proposed that this type of RNA-mediated defence mechanism is an ancient form of immunity to offset the transgene-, transposonand virus-mediated attack. However, whether 1) RNA silencing is a natural immune response in vertebrates to suppress pathogen invasion; or 2) vertebrate cells have evolved to counteract invasion in a 'RNA silencing' independent manner remains to be determined. A number of recent reports have provided tantalizing clues to support the view that RNA silencing functions as a physiological response to regulate viral infection in vertebrate cells. Amongst these, two manuscripts that are published in recent issues of Science and Immunity, respectively, have provided some of the first direct evidences that RNA silencing is an important component of antiviral defence in vertebrate cells. In addition to demonstrating RNA silencing to be critical to vertebrate innate immunity, these studies also highlight the potential of utilising virusinfection systems as models to refine our understanding on the molecular determinants of RNA silencing in vertebrate cells. RNA silencing was originally recognised as post-transcriptional gene silencing in plants (PTGS) [1], co-suppression in plants [2], or RNA-mediated virus resistance in plants [3]. It was subsequently understood that a similar mechanism (RNA interference) is also found in Caenorhabditis elegans [4] and fungi [5,6]. The generation of ~25 nucleotide RNA which pair to yield a ~19 base-pair double helix is the common denominator amongst these Published: 25 May 2005 Retrovirology 2005, 2:35 doi:10.1186/1742-4690-2-35 Received: 13 May 2005 Accepted: 25 May 2005 This article is available from: http://www.retrovirology.com/content/2/1/35 © 2005 Mak; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.