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J. Virol., Jan 1995, 213-221, Vol 69, No. 1
MN Pearson and GF Rohrmann
Homologous regions (hrs) were identified in the Lymantria dispar nuclear
polyhedrosis virus (LdMNPV) genome. A 1.58-kb region surrounding hr4 was
sequenced and found to have two distinct domains. Domain I (about 600 bp)
is composed of seven repeats of about 80 bp including a series of
palindromes containing MluI sites and overlapping XhoI and SacI sites.
Domain II (about 700 bp) is composed of eight partially repeated sequences
of 60 to 100 bp containing a 15- to 25-bp sequence that is 80 to 100% A+T
in addition to a 6- to 10-bp palindrome containing an NruI site.
Hybridization of a domain I sequence to cosmids containing the LdMNPV
genome indicated its presence at eight positions (hr1 to -8) on the genome.
In contrast, hybridization of domain II indicated that it was present only
at the hr4 locus. A DpnI- based transient-replication assay was used to
determine if subclones of hr4 transfected into LdMNPV-infected L. dispar
cells functioned as replication origins. Subclones of hr4 containing either
domain I or domain II replicated at very low or moderate levels,
respectively. However, when domain I and domain II were linked on the same
plasmid, high levels of replication were observed. A 1.4-kb region
containing hr1 was also sequenced. It lies immediately upstream of the
polyhedrin gene and contains six domain I-type repeats.
Four-hundred-base-pair regions of domain I repeats from hr1 and hr4 showed
89% sequence identity. Plasmids containing the hr1 domain I replicated at
low levels. However, hybrid plasmids in which the AT-rich hr4 domain II was
inserted adjacent to hr1 domain I replicated to high levels, indicating
that the AT-rich domain II greatly enhances replication. The orientation
and position of domains I and II relative to each other did not have major
effects on the levels of replication.
Copyright © 1995, American Society for Microbiology
Lymantria dispar nuclear polyhedrosis virus homologous regions: characterization of their ability to function as replication origins
Department of Agricultural Chemistry, Oregon State University, Corvallis 97331-7301.
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