title: Structural organization of DNA in chlorella viruses.
abstract: Chlorella viruses have icosahedral capsids with an internal membrane enclosing their large dsDNA genomes and associated proteins. Their genomes are packaged in the particles with a predicted DNA density of ca. 0.2 bp nm(-3). Occasionally infection of an algal cell by an individual particle fails and the viral DNA is dynamically ejected from the capsid. This shows that the release of the DNA generates a force, which can aid in the transfer of the genome into the host in a successful infection. Imaging of ejected viral DNA indicates that it is intimately associated with proteins in a periodic fashion. The bulk of the protein particles detected by atomic force microscopy have a size of ∼60 kDa and two proteins (A278L and A282L) of about this size are among 6 basic putative DNA binding proteins found in a proteomic analysis of DNA binding proteins packaged in the virion. A combination of fluorescence images of ejected DNA and a bioinformatics analysis of the DNA reveal periodic patterns in the viral DNA. The periodic distribution of GC rich regions in the genome provides potential binding sites for basic proteins. This DNA/protein aggregation could be responsible for the periodic concentration of fluorescently labeled DNA observed in ejected viral DNA. Collectively the data indicate that the large chlorella viruses have a DNA packaging strategy that differs from bacteriophages; it involves proteins and share similarities to that of chromatin structure in eukaryotes.
authors.affiliation: Plant Membrane Biophysics, Technische Universität Darmstadt, Darmstadt, Germany.
authors.forename: Timo
authors.initials: T
authors.lastname: Wulfmeyer
authors.forename: Christian
authors.initials: C
authors.lastname: Polzer
authors.forename: Gregor
authors.initials: G
authors.lastname: Hiepler
authors.forename: Kay
authors.initials: K
authors.lastname: Hamacher
authors.forename: Robert
authors.initials: R
authors.lastname: Shoeman
authors.forename: David D
authors.initials: DD
authors.lastname: Dunigan
authors.forename: James L
authors.initials: JL
authors.lastname: Van Etten
authors.forename: Marco
authors.initials: M
authors.lastname: Lolicato
authors.forename: Anna
authors.initials: A
authors.lastname: Moroni
authors.forename: Gerhard
authors.initials: G
authors.lastname: Thiel
authors.forename: Tobias
authors.initials: T
authors.lastname: Meckel
mesh_terms: D036022:Capsid Proteins; D002708:Chlorella / Q000821:virology*; D000460:Chlorophyta / Q000821:virology; D042003:DNA Packaging; D004279:DNA, Viral / Q000737:chemistry*; D004268:DNA-Binding Proteins / Q000737:chemistry; D005453:Fluorescence; D020862:GC Rich Sequence; D016679:Genome, Viral; D014764:Viral Proteins / Q000737:chemistry
chemical_list: D036022:Capsid Proteins; D004279:DNA, Viral; D004268:DNA-Binding Proteins; D014764:Viral Proteins