Structure and Expression of the Cauliflower Mosaic Virus Genome
Cauliflower mosaic virus (CaMV) is the type member of the caulimoviruses, the only plant viruses known to possess a double-stranded DNA genome (Shepherd, 1979). The genome of CaMV is circular and about 8000 bp in length. Two topologically distinct forms of CaMV DNA have been recognized. One such form is virion DNA, which contains three single-strand discontinuities, two in one strand and one in the other, at well defined sites on the circular DNA molecule (Hull and Howell, 1978; Volovitch et al., 1978). (Preparations of virion DNA also contain linear molecules but most of these are thought to arise from the circular form by adventitious breakage). The discontinuities in the circular virion DNA are not nicks or gaps but, rather, regions of sequence overlap where the 5’ and 3’ ends of the interrupted DNA strand overlap by 8 to 20 nucleotides (Richards et al., 1981). Consequently the DNA in the vicinity of each overlap is triple-stranded with one of the broken ends being displaced from its complementary strand by the other.
KeywordsSucrose Gradient Centrifugation Nuclease Digestion Supercoiled Form Nuclease Mapping Primer Extension Technique
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