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J. Virol., 08 1995, 4619-4627, Vol 69, No. 8
N Inoue and PE Pellett
We previously demonstrated by a DNA-binding assay that the human
herpesvirus 6B (HHV-6B) replication origin has a structure similar to those
of alphaherpesviruses, although the HHV-6B and herpes simplex virus type 1
(HSV-1) origin-binding proteins (OBPs) and origins are not interchangeable.
Here we describe additional properties of the interaction between HHV-6B
OBP and the HHV-6B origin. Competitive electrophoretic mobility shift
assays (EMSAs) with DNA duplexes containing single-base alterations allowed
deduction of a consensus DNA sequence for HHV-6B-specific OBP binding,
YGWYCWCCY, where Y is T or C and W is T or A, while that for HSV-1-specific
binding was reported to be YGYTCGCACT. By EMSA, the HHV-6B OBP DNA-binding
domain was mapped to a segment containing amino acids 482 to 770. However,
in Southwestern (protein-DNA) blotting, the region sufficient for the DNA
binding encompassed only amino acids 657 to 770. Similarly, Southwestern
blotting showed that amino acids 689 to 851 of HSV-1 OBP had HSV-1
origin-binding activity, although this region was insufficient for origin
binding in the EMSA. Although the longer DNA-binding domains identified by
EMSA have marginal overall homology among HHV-6B and alphaherpesvirus OBP
homologs, the smaller regions sufficient for the binding observed by
Southwestern blotting have significant similarity. From these results, we
propose a hypothesis that the DNA-binding domain of herpesvirus OBPs
consists of two subdomains, one containing a conserved motif that contacts
DNA directly, and another, less well conserved, that may modulate either
the conformation or accessibility of the binding domain.
Copyright © 1995, American Society for Microbiology
Human herpesvirus 6B origin-binding protein: DNA-binding domain and consensus binding sequence
National Institute of Health, Tokyo, Japan.
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