A potential role for RNA interference in controlling the activity of the human LINE-1 retrotransposon

Division of Molecular Biology, Beckman Research Institute of the City of Hope 1450 East Duarte Road, Duarte, CA 91010-3011, USA.
Nucleic Acids Research (Impact Factor: 9.11). 02/2005; 33(3):846-56. DOI: 10.1093/nar/gki223
Source: PubMed

ABSTRACT Long interspersed nuclear elements (LINE-1 or L1) comprise 17% of the human genome, although only 80-100 L1s are considered retrotransposition-competent (RC-L1). Despite their small number, RC-L1s are still potential hazards to genome integrity through insertional mutagenesis, unequal recombination and chromosome rearrangements. In this study, we provide several lines of evidence that the LINE-1 retrotransposon is susceptible to RNA interference (RNAi). First, double-stranded RNA (dsRNA) generated in vitro from an L1 template is converted into functional short interfering RNA (siRNA) by DICER, the RNase III enzyme that initiates RNAi in human cells. Second, pooled siRNA from in vitro cleavage of L1 dsRNA, as well as synthetic L1 siRNA, targeting the 5'-UTR leads to sequence-specific mRNA degradation of an L1 fusion transcript. Finally, both synthetic and pooled siRNA suppressed retrotransposition from a highly active RC-L1 clone in cell culture assay. Our report is the first to demonstrate that a human transposable element is subjected to RNAi.

Download full-text


Available from: John J Rossi, Jun 22, 2015
  • Source
    • "Secondly, retrotransposable elements are also susceptible to post-transcriptional regulation. For instance, endogenously encoded small interfering RNAs have been shown to reduce L1 retrotransposition in vitro (Soifer et al., 2005; Yang and Kazazian, 2006). Additionally, L1 transcripts that contain multiple polyadenylation signals lead to premature polyadenylation , resulting in the attenuation of L1 activity via truncation of its full-length transcripts (Perepelitsa-Belancio and Deininger, 2003). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Retroelements comprise a large and successful family of transposable genetic elements that, through intensive infiltration, have shaped the genomes of humans and other mammals over millions of years. In fact, retrotransposons now account for approximately 45% of the human genome. Because of their genomic mobility called retrotransposition, some retroelements can cause genetic diseases; such retrotransposition events occur not only in germ cells but also in somatic cells, posing a threat to genomic stability throughout all cellular populations. In response, mammals have developed intrinsic immunity mechanisms that provide resistance against the deleterious effects of retrotransposition. Among these, seven members of the APOBEC3 (A3) family of cytidine deaminases serve as highly active, intrinsic, antiretroviral host factors. Certain A3 proteins effectively counteract infections of retroviruses such as HIV-1, as well as those of other virus families, while also blocking the transposition of retroelements. Based on their preferential expression in the germ cells, in which retrotransposons may be active, it is likely that A3 proteins were acquired through mammalian evolution primarily to inhibit retrotransposition and thereby maintain genomic stability in these cells. This review summarizes the recent advances in our understanding of the interplay between the retroelements currently active in the human genome and the anti-retroelement A3 proteins.
    Frontiers in Microbiology 08/2012; 3:275. DOI:10.3389/fmicb.2012.00275 · 3.94 Impact Factor
  • Source
    • "). In human cell lines, transfected exogenous siRNAs can limit L1 expression (Soifer et al., 2005). But while TE-associated endogenous siRNAs have been reported in mammals, their formal involvement in host defense against TE invasion is still lacking. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Retrotransposable elements comprise around 50% of the mammalian genome. Their activity represents a constant threat to the host and has prompted the development of adaptive control mechanisms to protect genome architecture and function. To ensure their propagation, retrotransposons have to mobilize in cells destined for the next generation. Accordingly, these elements are particularly well suited to transcriptional networks associated with pluripotent and germinal states in mammals. The relaxation of epigenetic control that occurs in the early developing germline constitutes a dangerous window in which retrotransposons can escape from host restraint and massively expand. What could be observed as risky behavior may turn out to be an insidious strategy developed by germ cells to sense retrotransposons and hold them back in check. Herein, we review recent insights that have provided a detailed picture of the defense mechanisms that concur toward retrotransposon silencing in mammalian genomes, and in particular in the germline. In this lineage, retrotransposons are hit at multiple stages of their life cycle, through transcriptional repression, RNA degradation and translational control. An organized cross-talk between PIWI-interacting small RNAs (piRNAs) and various nuclear and cytoplasmic accessories provides this potent and multi-layered response to retrotransposon unleashing in early germ cells.
    Heredity 07/2010; 105(1):92-104. DOI:10.1038/hdy.2010.53 · 3.80 Impact Factor
  • Source
    • "However, the potential role of RNAi as a natural antiviral defence mechanism in mammalian cells remains controversial. The characteristic of antiviral RNAi—that is, accumulation of virusderived siRNAs—could not be identified in infected cells (Pfeffer et al, 2004); however, such molecules have been described more recently for several endogenous and exogenous viruses, including human immunodeficiency virus type 1 (HIV-1; Bennasser et al, 2005; Soifer et al, 2005; Yang & Kazazian, 2006; Parameswaran et al, 2008), and yet the significance of these findings is still being debated (Lin & Cullen, 2007). There is accumulating evidence that mammalian cells use microRNAs (miRNAs) to control viruses (Berkhout & Jeang, 2007). "
    [Show abstract] [Hide abstract]
    ABSTRACT: The question of whether RNA interference (RNAi) acts as an antiviral mechanism in mammalian cells remains controversial. The antiviral interferon (IFN) response cannot easily be distinguished from a possible antiviral RNAi pathway owing to the involvement of double-stranded RNA (dsRNA) as a common inducer molecule. The non-structural protein 3 (NS3) protein of rice hoja blanca virus (RHBV) is an RNA silencing suppressor (RSS) that exclusively binds to small dsRNA molecules. Here, we show that this plant viral RSS lacks IFN antagonistic activity, yet it is able to substitute the RSS function of the Tat protein of human immunodeficiency virus type 1. An NS3 mutant that is deficient in RNA binding and its associated RSS activity is inactive in this complementation assay. This cross-kingdom suppression of RNAi in mammalian cells by a plant viral RSS indicates the significance of the antiviral RNAi response in mammalian cells and the usefulness of well-defined RSS proteins.
    EMBO Reports 03/2009; 10(3):258-63. DOI:10.1038/embor.2009.6 · 7.86 Impact Factor
Show more