Aaron Irving

Publications

• 7.48

  Impact points

  Analysis of microRNA turnover in mammalian cells following Dicer1 ablation.

  Michael P Gantier, Claire E McCoy, Irina Rusinova, Damien Saulep, Die Wang, Dakang Xu, Aaron T Irving, Mark A Behlke, Paul J Hertzog, Fabienne Mackay, Bryan R G Williams

  Nucleic acids research. 03/2011; 39(13):5692-703.

  Although microRNAs (miRNAs) are key regulators of gene expression, little is known of their overall persistence in the cell following processing. Characterization of such persistence is key to the full appreciation of their regulatory roles. Accordingly, we measured miRNA decay rates in mouse embryo... [more] Although microRNAs (miRNAs) are key regulators of gene expression, little is known of their overall persistence in the cell following processing. Characterization of such persistence is key to the full appreciation of their regulatory roles. Accordingly, we measured miRNA decay rates in mouse embryonic fibroblasts following loss of Dicer1 enzymatic activity. The results confirm the inherent stability of miRNAs, the intracellular levels of which were mostly affected by cell division. Using the decay rates of a panel of six miRNAs representative of the global trend of miRNA decay, we establish a mathematical model of miRNA turnover and determine an average miRNA half-life of 119 h (i.e. ∼5 days). In addition, we demonstrate that select miRNAs turnover more rapidly than others. This study constitutes, to our knowledge, the first in-depth characterization of miRNA decay in mammalian cells. Our findings indicate that miRNAs are up to 10× more stable than messenger RNA and support the existence of novel mechanism(s) controlling selective miRNA cellular concentration and function.
• 6.89

  Impact points

  Genetic modulation of TLR8 response following bacterial phagocytosis.

  Michael P Gantier, Aaron T Irving, Maria Kaparakis-Liaskos, Dakang Xu, Vanessa A Evans, Paul U Cameron, James A Bourne, Richard L Ferrero, Matthias John, Mark A Behlke, Bryan R G Williams

  Human mutation. 09/2010; 31(9):1069-79.

  Human Toll-like receptors (TLRs) TLR7, TLR8, and TLR9 are important immune sensors of foreign nucleic acids encountered by phagocytes. Although there is growing evidence implicating TLR7 and TLR9 in the detection of intracellular pathogenic bacteria, characterization of such a role for TLR8 is curre... [more] Human Toll-like receptors (TLRs) TLR7, TLR8, and TLR9 are important immune sensors of foreign nucleic acids encountered by phagocytes. Although there is growing evidence implicating TLR7 and TLR9 in the detection of intracellular pathogenic bacteria, characterization of such a role for TLR8 is currently lacking. A recent genetic study has correlated the presence of a TLR8 single nucleotide polymorphism (SNP) (rs3764880:A>G; p.Met1Val) with the development of active tuberculosis, suggesting a role for TLR8 in the detection of phagosomal bacteria. Here we provide the first direct evidence that TLR8 sensing is activated in human monocytic cells following Helicobacter pylori phagocytosis. In addition, we show that rs3764880 fine tunes translation of the two TLR8 main isoforms, without affecting protein function. Although we show that TLR8 variant 2 (TLR8v2) is the prevalent form of TLR8 contributing to TLR8 function, we also uncover a role for the TLR8 long isoform (TLR8v1) in the positive regulation of TLR8 function in CD16(+)CD14(+) differentiated monocytes. Thus, TLR8 sensing can be activated following bacterial phagocytosis, and rs3764880 may play a role in the modulation of TLR8-dependent microbicidal response of infected macrophages.
• 6.24

  Impact points

  Rational design of immunostimulatory siRNAs.

  Michael P Gantier, Stephen Tong, Mark A Behlke, Aaron T Irving, Martha Lappas, Ulrika W Nilsson, Eicke Latz, Nigel A J McMillan, Bryan R G Williams

  Molecular therapy : the journal of the American Society of Gene Therapy. 04/2010; 18(4):785-95.

  Short-interfering RNAs (siRNAs) have engendered much enthusiasm for their ability to silence the expression of specific genes. However, it is now well established that siRNAs, depending on their sequence, can be variably sensed by the innate immune system through recruitment of toll-like receptors 7... [more] Short-interfering RNAs (siRNAs) have engendered much enthusiasm for their ability to silence the expression of specific genes. However, it is now well established that siRNAs, depending on their sequence, can be variably sensed by the innate immune system through recruitment of toll-like receptors 7 and 8 (TLR7/8). Here, we aimed to identify sequence-based modifications allowing for the design of bifunctional siRNAs with both proinflammatory and specific silencing activities, and with potentially increased therapeutic benefits. We found that the introduction of a micro-RNA (miRNA)-like nonpairing uridine-bulge in the passenger strand robustly increased immunostimulatory activity on human immune cells. This sequence modification had no effect on the silencing efficiency of the siRNA. Increased immunostimulation with the uridine-bulge design was specific to human cells, and conserved silencing efficiency required a Dicer-substrate scaffold. The increased cytokine production with the uridine-bulge design resulted in enhanced protection against Semliki Forest virus (SFV) infection, in viral assays. Thus, we characterize a design scaffold applicable to any given siRNA sequence, that results in increased innate immune activation without affecting gene silencing. Our data suggest that this sequence modification coupled with structural modification differentially recruits human TLR8 over TLR7, and could have potential application in antiviral therapies.

• Latest advances in innate antiviral defence.

  Aaron Irving, Bryan Rg Williams

  F1000 biology reports. 03/2009; 1:22.

  Recent identification of key components in the pattern recognition receptor pathway of retinoic acid-inducible gene-1-like receptors, coupled with characterisation of a new cytoplasmic DNA-sensing molecule, have led to a greater understanding of the role viral nucleic acids play in activating innate... [more] Recent identification of key components in the pattern recognition receptor pathway of retinoic acid-inducible gene-1-like receptors, coupled with characterisation of a new cytoplasmic DNA-sensing molecule, have led to a greater understanding of the role viral nucleic acids play in activating innate immunity. This activation of type I interferon is essential for both limiting viral infection and stimulating activation of the adaptive immune response.
• 3.45

  Impact points

  The development and future of oligonucleotide-based therapies for cervical cancer.

  Wenyi Gu, Lisa N Putral, Aaron Irving, Nigel A J McMillan

  Current opinion in molecular therapeutics. 05/2007; 9(2):126-31.

  Cervical cancer is an attractive model in which to test gene-specific therapies, because elimination of the HPV oncogenes E6 and E7 may result in cancer cell senescence. Oligonucleotide-based therapies tested over the years include antisense oligonucleotides, ribozymes and, more recently, small inte... [more] Cervical cancer is an attractive model in which to test gene-specific therapies, because elimination of the HPV oncogenes E6 and E7 may result in cancer cell senescence. Oligonucleotide-based therapies tested over the years include antisense oligonucleotides, ribozymes and, more recently, small interfering RNA (siRNA)-based treatments. The development and use of these technologies are reviewed. siRNA-based therapies have been touted as potential treatments for cancers, genetic disorders and viral infections and have a number of advantages over antisense and ribozyme technologies. As with the older technologies, in vitro testing of siRNAs against cervical cancer has shown promising results, however, the issues that held up the clinical development of ribozymes and antisense are currently also challenging the siRNA field; these are target selection, specificity and delivery. If these issues can be overcome, a range of new and potent therapies for cervical cancer could become available.

• Future of RNAi-based therapies for human papillomavirus-associated cervical cancer

  Jiezhong Chen, Aaron Irving, Nigel McMillan, Wenyi Gu

  Future Virology. 01/2007; 2:587-95.

  Over 99% of cervical cancers are associated with infection of high-risk type human papillomaviruses (HPV). These viruses infect epithelial cells lining the cervix and express the early viral genes E6 and E7, which are oncogenes and are primarily responsible for the transformation of the epithelial c... [more] Over 99% of cervical cancers are associated with infection of high-risk type human papillomaviruses (HPV). These viruses infect epithelial cells lining the cervix and express the early viral genes E6 and E7, which are oncogenes and are primarily responsible for the transformation of the epithelial cells. The continuous expression of those genes is essential for maintenance of the cancer cell phenotype and viability. These viral genes can be silenced using oligonucleotide-based techniques, for example RNAi, antisense RNA and ribozymes. In spite of promising results in vitro and in vivo, in mice, these methods have thus far proved unsuccessful in humans, owing to the lack of an effective delivery system amongst other limitations. In this review we will discuss potential gene-silencing strategies in cervical cancer that would target both viral genes such as E6 and E7, and cellular genes that become deregulated such as E2F, p53, Akt, mTor, NF-κB or Bcl-2. By investigating these approaches we may generate an effective treatment for HPV-induced cervical cancer using gene silencing.
• 1.63

  Impact points

  A novel method for screening viral interferon-resistance genes.

  Daniel T W Clarke, Aaron T Irving, Eleanore H Lambley, Elizabeth Payne, Nigel A J McMillan

  Journal of interferon & cytokine research : the official journal of the International Society for Interferon and Cytokine Research. 09/2004; 24(8):470-7.

  Many viruses have evolved mechanisms to antagonize the interferon (IFN) system, targeting all the major components involved in receptor binding and signaling. Although a number of these vital proteins are homologous to cellular proteins involved in IFN downregulation (e.g., viral IFN regulatory fact... [more] Many viruses have evolved mechanisms to antagonize the interferon (IFN) system, targeting all the major components involved in receptor binding and signaling. Although a number of these vital proteins are homologous to cellular proteins involved in IFN downregulation (e.g., viral IFN regulatory factors [vIRFs]), many share little resemblance to known proteins. To determine the IFN-blocking properties of these proteins, functional assays are required. Here, we present a new and rapid functional screening method, based on the 2fTGH cell line, which is able to determine viral gene products that inhibit the IFN-alpha/Jak-Stat signaling pathway. Expression cloning of viral IFN-blocking genes into 2fTGH and consequent selection with IFN-alpha and 6-thioguanine result in the outgrowth of cells that are no longer responsive to IFN-alpha. We also demonstrate that selection occurs if members of the Jak-Stat signaling pathway are lost. To show the utility of our system, we have used a known suppressor of IFN signaling, the human papillomavirus (HPV) E7 gene. Expression of E7 causes the loss of ability of 2fTGH cells to respond to IFN-alpha treatment because of a functional disruption of the signaling pathway. This approach offers a new strategy for identifying novel viral genes or new functions of already described viral genes that have a role in IFN-alpha signaling inhibition.

• Varicella-Zoster Virus evasion of the Interferon immune response

  Aaron Irving

  Many viruses have evolved mechanisms to antagonize the interferon (IFN) system, targeting all the major components involved in receptor binding and signalling. Although a number of these viral proteins are homologous to cellular proteins involved in IFN downregulation (e.g., viral IFN regulatory fac... [more] Many viruses have evolved mechanisms to antagonize the interferon (IFN) system, targeting all the major components involved in receptor binding and signalling. Although a number of these viral proteins are homologous to cellular proteins involved in IFN downregulation (e.g., viral IFN regulatory factors [vIRFs]), many share little resemblance to known proteins. To determine the IFN-blocking properties of these proteins, functional assays are required. Here, we present a new and rapid functional screening method, based on the 2FTGH cell line, which is able to determine viral gene products that inhibit the IFN-alpha/Jak-Stat signalling pathway. Expression cloning of viral IFN-blocking genes into 2FTGH and consequent selection with IFN-alpha and 6-thioguanine result in the outgrowth of cells that are no longer responsive to IFN-alpha. We also demonstrate that selection occurs if members of the Jak-Stat signalling pathway are lost. To show the utility of our system, we have used a known suppressor of IFN signalling, the human papillomavirus (HPV) E7 gene. Expression of E7 causes the loss of ability of 2FTGH cells to respond to IFN-alpha treatment because of a functional disruption of the signalling pathway. This approach offers a new strategy for identifying novel viral genes or new functions of already described viral genes that have a role in IFN-alpha signalling inhibition.