monitor biology DDT Vol. 9, No. 19 October 2004 1359-6446/04/$ – see front matter ©2004 Elsevier Ltd. All rights reserved. PII: S1359-6446(04)03188-5 856 design of gene-targeted drugs [5–7]. The promise of this technology rests on the expectation that synthetic ‘ gene- blocking’ oligomers, which have a sequence that is complementary to corresponding mRNA or pre-mRNA targets, will become a generic therapy of the future for various diseases. After common oligonucleotides and their modified analogues, a third generation of antisense oligomers – the artificial DNA and RNA mimics – is emerging, with the peptide nucleic acid (PNA) oligomers showing significant promise [8]. Recent studies performed at ISIS Pharmaceuticals (http://www.isip.com) with the murine cellular receptor CD40, which has a key role in immune response, have demonstrated that specific downregulation of protein expression can be efficiently achieved with the PNA antisense inhibitor ISIS208529; this molecule targets the exon 6 splice junction within the primary CD40 transcript [9]. When delivered to murine cells (primary macrophages and lymphoma B-cells) by electroporation, binding of ISIS208529 interferes with pre-mRNA splicing and results in the accumulation of a defective protein that lacks the transmembrane domain. Conjugation of ISIS208529 with oligolysine yields an even more potent antisense drug, ISIS278647, which is effective in murine cells via ‘ free uptake’ (i.e. without transfection or electroporation). Importantly, cells that have been treated with PNA inhibitors exhibit a decrease in the CD40-mediated production of the cytokine interleukin-12 (IL-12) as a result of inhibition of the CD40-signalling pathway. These results show that antisense PNA oligomers can be employed as new immunomodulatory agents. Given that just a few antisense drugs have entered clinical trials [10], and with only one such drug currently approved for clinical use (antiviral vitravene or fomivirsen; ISIS2922), these novel drug candidates are valuable additions to the small antisense family. 5 Schiavone, N. et al. (2004) Antisense oligonucleotide drug design. Curr. Pharm. Des. 10, 769–784 6 Benimetskaya, L. and Stein, C.A. (2002) Antisense therapy: recent advances and relevance to prostate cancer. Clin. Prostate Cancer 1, 20–30 7 Crooke, S.T. (1999) Molecular mechanisms of action of antisense drugs. Biochim. Biophys. Acta 1489, 31–44 8 Demidov, V.V. (2002) PNA comes of age: from infancy to maturity. Drug Discov. Today 7, 153–155 9 Siwkowski, A.M. et al. (2004) Identification and functional validation of PNAs that inhibit murine CD40 expression by redirection of splicing. Nucleic Acids Res. 32, 2695–2706 10 Filmore, D. (2004) Assessing antisense. Modern Drug Discov. 7, 49–50 Vadim V. Demidov vvd@bu.edu www.drugdiscoverytoday.com Biology Novel Streptococcus pyogenes exotoxin disrupts cytoskeleton Exotoxins with ADP-ribosyltransferase (ADPRT) activity are produced by many bacterial pathogens. ADPRTs transfer ADP- ribose from β-NAD + onto host target proteins such as transcription factors, signaling molecules, and cytoskeletal proteins and thereby interfere with their function. In the important human pathogen Streptococcus pyogenes there are two known ADPRTs (GAPDH and SPN), but no cellular targets have been identified. Coye et al. identified a novel putative ADPRT, SpyA, which is present in several genomes of various serotypes [ 1]. Recombinantly expressed SpyA, but not SpyA mutated in a putatively catalytic glutamic acid residue, has NAD- glycohydrolase activity and ribosylates poly-L-arginine. Besides auto-ribosylation, SpyA ribosylates several proteins when incubated with cellular extracts. Two- dimensional electrophoresis and mass spectroscopy identified the cytoskeletal proteins actin, vimentin and tropomyosin as SpyA targets. Expression of SpyA in HeLa cells and fluorescence microscopy demonstrated that actin microfilaments were disrupted. The authors hypothesize that this modification could interfere with phagocytosis of the bacteria by professional phagocytes. It is still unclear how SpyA enters host cells, but the authors speculate that cytolysin mediated translocation, which is crucial for delivery of SPN, could be involved. Another possibility not mentioned in this paper is that SpyA could be expressed by intracellular bacteria within the phagocytes and contribute to survival by cytoskeletal rearrangements. This study describes a novel ADP- ribosyltransferase and for first time identifies cellular targets for an ADPRT from S. pyogenes. Even though there are still several questions to be answered regarding in vivo expression and cellular translocation/intracellular expression, this report indicates that SpyA and other ADPRTs could be important for the molecular pathogenesis of S. pyogenes. 1 Coye, L.H. and Collins, C.M. (2004) Identification of SpyA, a novel ADP- ribosyltransferase of Streptococcus pyogenes, Mol. Microbiol. doi:10.1111/j.1365- 2958.2004.04262.x. (EPub. ahead of print; http://blackwell-synergy.com) Mattias Collin collinm@mail.rockefeller.edu A bit of Lov for HIV-1 patients HIV-1 entry into and exit from target cells requires adequate cholesterol levels in host and viral membranes. Protein co- aggregation is also needed at the host cell surface: CD4 and chemokine receptors for entry, Gag and gp160 for budding. The HIV-1 infection process induces receptors clustering with lipid rafts, which necessitates actin cytoskeleton rearrangements. Rho is suspected to play a key role during this reorganization process. Del Real et al. now provide evidence that statins prevent HIV-1 infection in cultured primary cells, in animal models and in chronically infected individuals [ 2]. Statins, currently used to treat hypercholesterolemia, inhibit 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase. HMG- CoA reductase produces mevalonic acid, a precursor for cholesterol. Microbiology