Location of Homologous DNA Sequences Interspersed at Five Regions in the Baculovirus AcMNPV Genome

Abstract

An examination of Autographa californica nuclear polyhedrosis virus DNA revealed the presence of five interspersed regions, rich in Eco RI restriction sites, which shared homologous sequences. These homologous regions (hr), designated hr 1 to hr 5 , occur at or near the following Eco RI fragment junctions: hr 1 Eco RI-B— Eco RI-I (0.0 map units); hr 2 , Eco RI-A— Eco RI-J (19.8 map units); hr 3 , Eco RI-C— Eco RI-G (52.9 map units); hr 4 , Eco RI-Q— Eco RI-L (69.8 map units); and hr 5 , Eco RI-S— Eco RI-X (88.0 map units). Four of these regions were identified, by cross-blot hybridization of Hin dIII-restricted A. californica nuclear polyhedrosis virus DNA, to be within the Hin dIII-A/B, -F, -L, and -Q fragments. The location of these regions and the identification of a fifth homologous region were confirmed, and their characterization was facilitated, by using two plasmids with Hin dIII-L or -Q fragment insertions, which contained the homologous regions hr 2 and hr 5 , respectively. The sizes of the homologous regions were about 800 base pairs for hr 2 , 500 base pairs for hr 5 , and less than 500 base pairs for hr 1 , hr 3 , and hr 4 . A set of small Eco RI fragments ( Eco RI minifragments) which ranged in size from 225 to 73 base pairs were detected in A. californica nuclear polyhedrosis virus DNA and Hin dIII-L and -Q fragments by polyacrylamide gel analysis. Some of the minifragments in viral DNA were present in extramolar amounts and corresponded in size to some of the minifragments present in Hin dIII-L and -Q. Clones of some of the Eco RI minifragments were used as probes in hybridizations to digests of viral DNA and of Hin dIII-L and -Q. The hybridization data, obtained under various levels of stringency, suggested that there was a degree of mismatching between the sequences which were responsible for the homology.