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      The crystal structure of the DNA-binding domain of vIRF-1 from the oncogenic KSHV reveals a conserved fold for DNA binding and reinforces its role as a transcription factor

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          Abstract

          Kaposi’s sarcoma-associated herpesvirus encodes four viral homologues to cellular interferon regulatory factors (IRFs), where the most studied is vIRF-1. Even though vIRF-1 shows sequence homology to the N-terminal DNA-binding domain (DBD) of human IRFs, a specific role for this domain in vIRF-1’s function has remained uncertain. To provide insights into the function of the vIRF-1 DBD, we have determined the crystal structure of it in complex with DNA and in its apo-form. Using a thermal stability shift assay (TSSA), we show that the vIRF-1 DBD binds DNA, whereas full-length vIRF-1 does not, suggesting a cis-acting regulatory mechanism in similarity to human IRFs. The complex structure of vIRF-1 DBD reveals interactions with the DNA backbone and the positioning of two arginines for specific recognition in the major grove. A superimposition with human IRF-3 reveals a similar positioning of the two specificity-determining arginines, and additional TSSAs indicate binding of vIRF-1 to an IRF-3 operator consensus sequence. The results from this study, therefore, provide support that vIRF-1 has evolved to bind DNA and plays a role in DNA binding in the context of transcriptional regulation and might act on some of the many operator sequences controlled by human IRF-3.

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          Most cited references47

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          Identification of herpesvirus-like DNA sequences in AIDS-associated Kaposi's sarcoma.

          Representational difference analysis was used to isolate unique sequences present in more than 90 percent of Kaposi's sarcoma (KS) tissues obtained from patients with acquired immunodeficiency syndrome (AIDS). These sequences were not present in tissue DNA from non-AIDS patients, but were present in 15 percent of non-KS tissue DNA samples from AIDS patients. The sequences are homologous to, but distinct from, capsid and tegument protein genes of the Gammaherpesvirinae, herpesvirus saimiri and Epstein-Barr virus. These KS-associated herpesvirus-like (KSHV) sequences appear to define a new human herpesvirus.
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            The IRF family transcription factors in immunity and oncogenesis.

            The interferon regulatory factor (IRF) family, consisting of nine members in mammals, was identified in the late 1980s in the context of research into the type I interferon system. Subsequent studies over the past two decades have revealed the versatile and critical functions performed by this transcription factor family. Indeed, many IRF members play central roles in the cellular differentiation of hematopoietic cells and in the regulation of gene expression in response to pathogen-derived danger signals. In particular, the advances made in understanding the immunobiology of Toll-like and other pattern-recognition receptors have recently generated new momentum for the study of IRFs. Moreover, the role of several IRF family members in the regulation of the cell cycle and apoptosis has important implications for understanding susceptibility to and progression of several cancers.
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              IRF family of transcription factors as regulators of host defense.

              Interferon regulatory factors (IRFs) constitute a family of transcription factors that commonly possess a novel helix-turn-helix DNA-binding motif. Following the initial identification of two structurally related members, IRF-1 and IRF-2, seven additional members have now been reported. In addition, virally encoded IRFs, which may interfere with cellular IRFs, have also been identified. Thus far, intensive functional analyses have been done on IRF-1, revealing a remarkable functional diversity of this transcription factor in the regulation of cellular response in host defense. Indeed, IRF-1 selectively modulates different sets of genes, depending on the cell type and/or the nature of cellular stimuli, in order to evoke appropriate responses in each. More recently, much attention has also been focused on other IRF family members. Their functional roles, through interactions with their own or other members of the family of transcription factors, are becoming clearer in the regulation of host defense, such as innate and adaptive immune responses and oncogenesis.
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                Author and article information

                Journal
                Nucleic Acids Res
                Nucleic Acids Res
                nar
                nar
                Nucleic Acids Research
                Oxford University Press
                0305-1048
                1362-4962
                April 2013
                21 February 2013
                21 February 2013
                : 41
                : 7
                : 4295-4306
                Affiliations
                1Division of Structural Biology and Biochemistry, School of Biological Sciences, Nanyang Technological University, 138673 Singapore, Singapore and 2Division of Biophysics, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm SE-171 11, Sweden
                Author notes
                *To whom correspondence should be addressed. Tel: +65 65869673; Fax: +65 67791117; Email: pnordlund@ 123456ntu.edu.sg
                Correspondence may also be addressed to Sue-Li Dahlroth. Tel: +65 65869658; Fax: +65 67791117; Email: sdahlroth@ 123456ntu.edu.sg
                Article
                gkt082
                10.1093/nar/gkt082
                3627575
                23435230
                ee7fc61c-6867-45ad-8f5e-5f0d279aca6d
                © The Author(s) 2013. Published by Oxford University Press.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( http://creativecommons.org/licenses/by-nc/3.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 17 October 2012
                : 22 January 2013
                : 22 January 2013
                Page count
                Pages: 12
                Categories
                Structural Biology

                Genetics
                Genetics

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