Indexed on: 01 Nov '92Published on: 01 Nov '92Published in: Virus Genes
The structure of the third origin of DNA replication (CIV-ori-M) of the genome (209 kbp) of Chilo iridescent virus (CIV) was determined by DNA nucleotide sequence analysis. The CIV-ori-M is located within the DNA sequences of theEcoRI CIV DNA fragment M (7 kbp; 0.310–0.345 viral map units) between the genome coordinates 0.310 (EcoRI site) and 0.317 (NcoI site). The DNA nucleotide sequence of theEcoRI/NcoI CIV DNA fragment (1601 bp) was determined for identifying the DNA sequence of the corresponding origin of DNA replication. The analysis of the DNA sequences of this region revealed the presence of a 12-mer inverted repeat at nucleotide positions 485–496 and 503–513 (485-AGATATTTGACT-496-TATGT-503-AGTCAAATATCT-513) that are able to form a hairpin-loop structure. A double-stranded DNA fragment was synthesized that corresponds to the nucleotide positions 485–513 that were cloned into the phages M13mp18 and M13mp19, and were screened for their ability to be amplified in CF-124 cell cultures infected with CIV. The successful amplification of the DNA sequence of the CIV-ori-M is strong evidence that this particular region of the CIV genome indeed serves as the origin of DNA replication.The analysis of the DNA sequence of CIV-ori-M in comparison to the DNA sequence of the two other characterized origins of DNA replication (CIV-ori-H and Y) of the CIV genome (9) was carried out, and the results are shown in Table 2. According to these data the DNA sequence homology between the DNA sequences of the CIV-ori-M and CIV-ori-Y, and between the CIV-ori-M or CIV-ori-H, was found to be 58% and 55%, respectively.