Paula Traktman, PhD
Walter Schroeder Professor and Chairman
Microbiology and Molecular Genetics
Medical College of Wisconsin
Research Focus: Kinases, phosphatases, and polymerases: vaccinia virus and its interaction with the host
PhD: Massachusetts Institute of Technology (1981) Biology
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Vaccinia virus replicates solely within the cytoplasm of infected cells, and the 192 kb DNA genome encodes most, if not all, of the functions required for such processes as gene expression, DNA replication, and virion assembly. We have focused our attention primarily on viral DNA replication, the role of virally encoded kinases and phosphatases within the infectious cycle, and virion morphogenesis. Our work integrates diverse approaches drawn from the disciplines of virology, molecular genetics, cell biology, and biochemistry.
With regard to DNA replication, we are interested in understanding the mechanism of replication, as well as pursuing a biochemical and genetic investigation of the proteins involved. Using recombinant minichromosomes, we have shown that 200bp of viral telomeric DNA are sufficient to generate an efficiently replicating template. Dissection of these sequences, and attempts to identify proteins which interact with them, will be undertaken. The core of the replication machinery itself is the viral DNA polymerase, and we have been focusing on how the polymerase (the E9 protein), the viral A20 protein, and the viral uracil DNA glycosylase (UDG, the D4 protein) work together to accomplish processive DNA synthesis. The participation of UDG, which is an enzyme more commonly associated with DNA repair, in the constitution of the processive polymerase is a novel feature of the viral system. We are also characterizing a virally encoded ss-DNA binding protein (I3) and the D5 protein, an NTPase whose sequence has the hallmarks of a superfamily III helicase. Our goal is to fully understand how these proteins function coordinately to accomplish faithful and efficient DNA synthesis. Finally, we are studying how the interaction of the viral genome with the I6 telomere-binding protein enables the encapsidation of the genome into nascent virions.
Our studies have shown that the viral B1 protein kinase also plays an essential role in viral DNA replication. We are attempting to find both viral and cellular substrates of B1 that will elucidate its role in DNA replication. As part of these studies, we have become involved in an analysis of a family of cellular protein kinases known as VRK (vaccinia related kinases) 1,2 and 3. As their name implies, these proteins have significant sequence similarity to the viral B1 kinase, and we have shown that VRK1 can complement the replication defect of a virus encoding a defective B1 protein. We are engaged in studying the structure and function of the VRK1 kinases, both in tissue culture and in genetically targeted mice.
We are also interested in the structure and function of the viral H1 phosphatase and F10 kinase. Using a recombinant viral construct in which the H1 phosphatase is under experimental control, we have demonstrated that the phosphatase plays an essential role in ensuring the structural integrity, transcriptional competence, and infectivity of nascent virions. We are collaborating with a biotech company to search for small molecule inhibitors of H1 that might serve as antiviral compounds. We have shown that the F10 kinase is at the top of the hierarchy of proteins that drive the process of virion morphogenesis. F10 is a dual specificity kinase that can phosphorylate serine, threonine and tyrosine residues; we have also shown that it can bind to phosphoinositides in vitro and associate with membranes in vivo. When F10 is repressed or inactivated, virion morphogenesis arrests at a very early stage as visualized by electron microscopy. We have identified several viral substrates of the F10 kinase, and have in turn used genetic and cell biological approaches to characterize these proteins and their roles in virion morphogenesis. We are also trying to identify the source of the membranes used to generate nascent virions: are they assembled de novo or diverted from an intracellular organelle? The process of virion assembly involves a cascade of protein/protein, protein/DNA, and protein/lipid interactions; it serves as an excellent model system for the process of cellular organelle biogenesis.
Recent Publications
Wiebe MS, Traktman P. Poxviral B1 kinase overcomes barrier to autointegration factor, a host defense, against virus replication. Cell Host & Microbe. 2007 May;1(3):187-197.
Abstract
Boyle KA, Arps L, Traktman P. Biochemical and genetic analysis of the vaccinia virus D5 protein: multimerization-dependent ATPase activity is required to support viral DNA replication. J Virol. 2007 Jan;81(2):844-59. Epub 2006 Nov 8.
Abstract
Condit RC, Moussatche N, Traktman P. In a nutshell: structure and assembly of the vaccinia virion. Adv Virus Res. 2006;66:31-124. Review.
Abstract
Nichols RJ, Wiebe MS, Traktman P. The vaccinia-related kinases phosphorylate the N' terminus of BAF, regulating its interaction with DNA and its retention in the nucleus. Mol Biol Cell. 2006 May;17(5):2451-64. Epub 2006 Feb 22.
Abstract
Stanitsa ES, Arps L, Traktman P. The vaccinia virus uracil DNA glycosylase interacts with the A20 protein to form a heterodimeric processivity factor for the viral DNA polymerase. J Biol Chem. 2006 Feb 10;281(6):3439-51. Epub 2005 Dec 1.
Abstract
Mercer J, Traktman P. Genetic and cell biological characterization of the vaccinia virus A30 and G7 phosphoproteins. J Virol. 2005 Jun;79(11):7146-61.
Abstract
Punjabi A, Traktman P. Cell Biological and Functional Characterization of the Vaccinia Virus F10 Kinase: Implications for the Mechanism of Virion Morphogenesis. J Virol. 2005 Feb;79(4):2171-2190.
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Lefkowitz EJ, Upton C, Changayil SS, Buck C, Traktman P, Buller RM. Poxvirus Bioinformatics Resource Center: a comprehensive Poxviridae informational and analytical resource. Nucleic Acids Res. 2005 Jan 1;33 Database Issue:D311-6.
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Unger B, Traktman P. Vaccinia virus morphogenesis: A13 phosphoprotein is required for assembly of mature virions. J Virol. 2004 Aug;78(16):8885-901.
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Traktman P, Boyle K. Methods for analysis of poxvirus DNA replication. Methods Mol Biol. 2004;269:169-86. Review.
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Boyle KA, Traktman P. Members of a novel family of mammalian protein kinases complement the DNA-negative phenotype of a vaccinia virus ts mutant defective in the B1 kinase. J Virol. 2004 Feb;78(4):1992-2005.
Abstract
Nichols RJ, Traktman P. Characterization of three paralogous members of the Mammalian vaccinia related kinase family. J Biol Chem. 2004 Feb 27;279(9):7934-46. Epub 2003 Nov 25.
Abstract
Grubisha O, Traktman P. Genetic analysis of the vaccinia virus I6 telomere-binding protein uncovers a key role in genome encapsidation. J Virol. 2003 Oct;77(20):10929-42.
Abstract
Mercer J, Traktman P. Investigation of structural and functional motifs within the vaccinia virus A14 phosphoprotein, an essential component of the virion membrane. J Virol. 2003 Aug;77(16):8857-71.
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Lerch-Gaggl A, Haque J, Li J, Ning G, Traktman P, Duncan SA. Pescadillo is essential for nucleolar assembly, ribosome biogenesis, and mammalian cell proliferation. J Biol Chem. 2002 Nov 22;277(47):45347-55. Epub 2002 Sep 16.
Abstract
Punjabi A, Boyle K, DeMasi J, Grubisha O, Unger B, Khanna M, Traktman P. Clustered charge-to-alanine mutagenesis of the vaccinia virus A20 gene: temperature-sensitive mutants have a DNA-minus phenotype and are defective in the production of processive DNA polymerase activity. J Virol. 2001 Dec;75(24):12308-18.
Abstract
Klemperer N, McDonald W, Boyle K, Unger B, Traktman P. The A20R protein is a stoichiometric component of the processive form of vaccinia virus DNA polymerase. J Virol. 2001 Dec;75(24):12298-307.
Abstract
DeMasi J, Du S, Lennon D, Traktman P. Vaccinia virus telomeres: interaction with the viral I1, I6, and K4 proteins. J Virol. 2001 Nov;75(21):10090-105.
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Najarro P, Traktman P, Lewis JA. Vaccinia virus blocks gamma interferon signal transduction: viral VH1 phosphatase reverses Stat1 activation. J Virol. 2001 Apr;75(7):3185-96.
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Traktman P, Liu K, DeMasi J, Rollins R, Jesty S, Unger B. Elucidating the essential role of the A14 phosphoprotein in vaccinia virus morphogenesis: construction and characterization of a tetracycline-inducible recombinant. J Virol. 2000 Apr;74(8):3682-95.
Abstract
Contact Information
Email:
ptrakt@mcw.edu
Phone: 414-456-8253 (Department)
Room: BSB-273