The Cauliflower Mosaic Virus Minichromosome
Plant viruses which contain DNA genomes have recently gained popularity as potential vehicles for introducing foreign DNA into plants (reviewed by Howell, 1982; Hohn et al., 1982). The most intensively studied of these DNA viruses is cauliflower mosaic virus (CaMV) which contains a double-stranded DNA genome of about 8 kilobases. The infective DNA purified from virus particles is circular, but not covalently closed (i.e., generally two to three site-specific discontinuities occur in the genome; Hull and Howell, 1978; Volovitch et al., 1978). One of the discontinuities occurs in the α-strand of CaMV DNA and is generally considered as map position 0/1 on the circular genome. The complementary or β-strand of CaMV DNA usually contains two discontinuities at map positions 0.20 and 0.53. In one case, however, the CM4-184 isolate of CaMV contains a deletion of about 421 base pairs in and around map position 0.20 which eliminates one of the discontinuities in the α-strand. In the virus particle, the DNA is surrounded by a protein capsid shell (reviewed by Hohn et al., 1982), but additional proteins such as histones or other chromosomal proteins are not associated with the encapsidated DNA.
KeywordsCauliflower Mosaic Virus Transcription Complex Subunit Structure Circular Genome Cesium Chloride Density Gradient
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