Arch Virol (2001) 146: 403–413
Characterization of Kaposi’s sarcoma-associated
herpesvirus/human herpesvirus-8 ORF57 promoter
,and C. Wood
School of Biological Sciences, University of Nebraska, Lincoln, Nebraska, U.S.A.
Center for Biological Chemistry, University of Nebraska, Lincoln, Nebraska, U.S.A.
Accepted June 22, 2000
Summary. Kaposi’s sarcoma-associated herpesvirus (KSHV) is a recently dis-
covered human gamma herpesvirus (HHV-8) that plays an important role in Ka-
posi’s sarcoma development. Here, we further characterize the regulation of the
early HHV-8 gene, open reading frame 57 (ORF57). ORF57 is a spliced gene
consisting of two exons with a 108-bp intron near the 5
end. The ORF57 mRNA
can potentially be initiated at two different start sites, and its expression can be
signiﬁcantly stimulated by ORF50, an HHV-8 immediate early gene. The target
site for ORF50 transactivation was mapped to a 40-bp fragment compassing nt
81904 to 81943 in the ORF57 promoter. Our study on the regulation of ORF57
expression by ORF50 provides the basis for further studies on the regulation of
HHV-8 lytic gene expression.
Kaposi’s sarcoma-associated herpesvirus (KSHV), also known as human her-
pesvirus 8 (HHV-8), is the most recently identiﬁed human gamma herpesvirus
[5, 6]. Sequence analysis indicated that it has signiﬁcant sequence homology
with the Epstein-Barr virus (EBV) and herpesvirus saimiri (HVS) [1, 4, 15, 20].
The genomes of EBV, HVS and HHV-8 are considered to be generally co-linear,
having homologous sequences in relatively similar locations [1, 4, 9, 15, 18].
The expression of herpesvirus genes during lytic infection is sequentially
regulated. There are several early regulatory genes identiﬁed in all classes of her-
The ﬁrst two authors contributed equally to this study.