Arch Virol (1997) 142: 193—204
Comparison of a 20 kb region of human herpesvirus 6B
with other human betaherpesviruses reveals conserved
replication genes and adjacent divergent open reading frames
G. J. Lindquester
, C. A. Greenamoyer
, E. D. Anton
, J. J. O’Brian
P. E. Pellett
, and T. R. Dambaugh
Department of Biology, Rhodes College, Memphis, Tennessee, U.S.A.
Centers for Disease Control and Prevention, Atlanta, Georgia, U.S.A.
DuPont Merck Pharmaceuticals Co., Wilmington, Delaware, U.S.A.
Accepted July 30, 1996
Summary. The sequence of a 20.15 kb region from human herpesvirus 6 variant
B (HHV-6B) strain Z29 is described (GenBank accession number L14772).
Determinations of protein homologies for seventeen predicted gene products
revealed HHV-6B homologs of six proteins well-conserved both in genetic
context and amino acid sequence throughout the alpha-, beta-, and gammaher-
pesvirus subfamilies. These include proteins involved in viral DNA replication,
packaging and nucleotide metabolism, and conserved proteins of undeﬁned
function. The close evolutionary relationship of the human betaherpesviruses,
HHV-6B, HHV-6A, HHV-7 and human cytomegalovirus (HCMV) was con-
ﬁrmed by identiﬁcation of several protein sequences encoded only by these
viruses, including homologs of the HCMV early phosphoprotein family and
a series of HCMV open reading frames predicted to encode glycoprotein exons.
Homologs of essential HSV-1 replication proteins, UL8 and UL9, were also
identiﬁed. Downstream from the conserved replication locus, each betaherpes-
virus contains a region of divergent, small open reading frames. The evolution of
this region and its potential use in the development of a viral vector system are
Human herpesvirus 6 (HHV-6) was initially isolated from adults with diverse
lymphoproliferative diseases. Subsequent studies revealed that seroconversion
with HHV-6 generally occurs within the ﬁrst year of life with greater than 90%
antibody prevalence by age three years. HHV-6 isolates can be classiﬁed into