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Báo cáo khoa học: Identification of the heparin-binding domains of the interferon-induced protein kinase, PKR

PKR is an interferon-induced serine-threonine protein kinase that plays an important role in the mediation of the antiviral and antiproliferative actions of interferons. PKR is present at low basal levels in cells and its expression is induced at the transcriptional level by interferons. PKR’s kin-ase activity stays latent until it binds to its activator. In the case of virally infected cells, double-stranded (ds) RNA serves as PKR’s activator. | ềFEBS Journal Identification of the heparin-binding domains of the interferon-induced protein kinase PKR Stephen Fasciano Brian Hutchins Indhira Handy and Rekha C. Patel Department of BiologicalSciences University of South Carolina Columbia SC USA Keywords domain mapping dsRNA heparin interferon protein kinase Correspondence R. C. Patel Department of Biological Sciences University of South Carolina 700 Sumter Street Columbia SC 29208 USA Fax 1 803 777 4002 Tel 1 803 777 1853 E-mail patelr@sc.edu Received 1 November 2004 revised 5 January 2005 accepted 19 January 2005 doi 10.1111 j.1742-4658.2005.04575.x PKR is an interferon-induced serine-threonine protein kinase that plays an important role in the mediation of the antiviral and antiproliferative actions of interferons. PKR is present at low basal levels in cells and its expression is induced at the transcriptional level by interferons. PKR s kinase activity stays latent until it binds to its activator. In the case of virally infected cells double-stranded ds RNA serves as PKR s activator. The dsRNA binds to PKR via two copies of an evolutionarily conserved motif thus inducing a conformational change unmasking the ATP-binding site and leading to autophosphorylation of PKR. Activated PKR then phosphorylates the a-subunit of the protein synthesis initiation factor 2 eIF2a thereby inducing a general block in the initiation of protein synthesis. In addition to dsRNA polyanionic agents such as heparin can also activate PKR. In contrast to dsRNA-induced activation of PKR heparin-dependent PKR activation has so far remained uncharacterized. In order to understand the mechanism of heparin-induced PKR activation we have mapped the heparin-binding domains of PKR. Our results indicate that PKR has two heparin-binding domains that are nonoverlapping with its dsRNA-binding domains. Although both these domains can function independently of each other they function cooperatively when present together. Point mutations created .