Chlorella Viruses

Yamada Takashi

Onimatsu Hideki

Van Etten James L.

Advances in Virus Research

Chlorella viruses or chloroviruses are large, icosahedral, plaque-forming, double-stranded-DNA-containing viruses that replicate in certain strains of the unicellular green alga Chlorella. DNA sequence analysis of the 330-kbp genome of Paramecium bursaria chlorella virus 1 (PBCV-1), the prototype of this virus family (Phycodnaviridae), predict ∼366 protein-encoding genes and 11 tRNA genes. The predicted gene products of ∼500f these genes resemble proteins of known function, including many that are completely unexpected for a virus. In addition, the chlorella viruses have several features and encode many gene products that distinguish them from most viruses. These products include: (1) multiple DNA methyltransferases and DNA site-specific endonucleases, (2) the enzymes required to glycosylate their proteins and synthesize polysaccharides such as hyaluronan and chitin, (3) a virus-encoded K+ channel (called Kcv) located in the internal membrane of the virions, (4) a SET domain containing protein (referred to as vSET) that dimethylates Lys27 in histone 3, and (5) PBCV-1 has three types of introns; a self-splicing intron, a spliceosomal processed intron, and a small tRNA intron. Accumulating evidence indicates that the chlorella viruses have a very long evolutionary history. This review mainly deals with research on the virion structure, genome rearrangements, gene expression, cell wall degradation, polysaccharide synthesis, and evolution of PBCV-1 as well as other related viruses.

Chlorella viruses

PBCV-1

virion structure

gene expression

genome rearrangements

polysaccharide synthesis and degradation

Biology [ 460 ]

eng

Elsevier Inc.

Copyright (c) 2006 Elsevier Inc.

[ISSN] 0065-3527

[DOI] 10.1016/S0065-3527(06)66006-5

[NCID] AA00514058

[PMID] 16877063

[DOI] http://dx.doi.org/10.1016/S0065-3527(06)66006-5 isVersionOf