Human herpesvirus 6 (strain U1102) encodes homologues of the conserved herpesvirus glycoprotein gM and the alphaherpesvirus origin-binding protein

272

159

Human herpesvirus 7 (HHV-7) is a recently isolated betaherpesvirus that is prevalent in the human population, with primary infection usually occurring in early childhood. HHV-7 is related to human herpesvirus 6 (HHV-6) in terms of both biological and, from limited prior DNA sequence analysis, genetic criteria. However, extensive analysis of the HHV-7 genome has not been reported, and the precise phylogenetic relationship of HHV-7 to the other human betaherpesviruses HHV-6 and human cytomegalovirus has not been determined. Here I report on the determination and analysis of the complete DNA sequence of HHV-7 strain JI. The data establish that the close biological relationship of HHV-6 and HHV-7 is reflected at the genetic level, where there is a very high degree of conservation of genetic content and encoded amino acid sequences. The data also delineate loci of divergence between the HHV-6 and HHV-7 genomes, which occur at the genome termini in the region of the terminal direct-repeat elements and within limited regions of the unique component. Of potential significance with respect to biological and evolutionary divergence of HHV-6 and HHV-7 are notable structural differences in putative transcriptional regulatory genes specified by the direct-repeat and immediate-early region A loci of these viruses and the absence of an equivalent of the HHV-6 adeno-associated virus type 2 rep gene homolog in HHV-7.

Section: Resultsmentioning

confidence: 99%

Determination and analysis of the complete nucleotide sequence of human herpesvirus

Nicholas¹

1996

272

159

“…Sequence analyses of HHV-6 strains (U1102, Z29, and HST) (10,13,16) revealed that the overall arrangement of the HHV-6 genes is similar to that of human cytomegalovirus (HCMV), with which it shares 66% sequence identity (28); therefore, HHV-6 has been classified as a betaherpesvirus. HHV-6 can be further subdivided into two distinct groups, variants A and B (16).…”

mentioning

confidence: 99%

Characterization of the Human Herpesvirus 6 U69 Gene Product and Identification of Its Nuclear Localization Signal

Isegawa¹,

Miyamoto²,

Yasuda³

et al. 2008

To elucidate the function of the U69 protein kinase of human herpesvirus 6 (HHV-6) in vivo, we first analyzed its subcellular localization in HHV-6-infected Molt 3 cells by using polyclonal antibodies against the U69 protein. Immunofluorescence studies showed that the U69 signal localized to the nucleus in a mesh-like pattern in both HHV-6-infected and HHV6-transfected cells. A computer program predicted two overlapping classic nuclear localization signals (NLSs) in the N-terminal region of the protein; this NLS motif is highly conserved in the N-terminal region of most of the herpesvirus protein kinases examined to date. An N-terminal deletion mutant form of the protein failed to enter the nucleus, whereas a fusion protein of green fluorescent protein (GFP) and/or glutathione S-transferase (GST) and the U69 N-terminal region was transported into the nucleus, demonstrating that the predicted N-terminal NLSs of the protein actually function as NLSs. The nuclear transport of the GST-GFP fusion protein containing the N-terminal NLS of U69 was inhibited by wheat germ agglutinin and by the Q69L Ran-GTP mutant, indicating that the U69 protein is transported into the nucleus from the cytoplasm via classic nuclear transport machinery. A cell-free import assay showed that the nuclear transport of the U69 protein was mediated by importin ␣/␤ in conjunction with the small GTPase Ran. When the import assay was performed with a low concentration of each importin-␣ subtype, NPI2/importin-␣7 elicited more efficient transport activity than did Rch1/importin-␣1 or Qip1/importin-␣3. These results suggest a relationship between the localization of NPI2/importin-␣7 and the cell tropism of HHV-6.

“…Roseoloviruses each encode a homolog of the alphaherpesvirus OBP (14,16,23), which has no homolog in the cytomegaloviruses. The most extensively characterized alphaherpesvirus OBP, herpes simplex virus type 1 (HSV-1) OBP (OBP H1 ), binds as a dimer at each of two sites in its origins of replication (Box sites I and II in each ori S and two Box I sites in ori L ) (17).…”

Section: Human Herpesvirus 7 (Hhv-7) Is a Widely Prevalent Betaherpesmentioning

confidence: 99%

“…The minimal oriLyt regions of the cytomegaloviruses are long (Ͼ1.3-kb) complex structures consisting of multiple inverted and direct repeats, in addition to numerous transcription factor recognition sites that are believed to mediate activation of the replication origin (2,20,21,28). Unlike the cytomegaloviruses, oriLyts of HHV-6A and HHV-6B have features in common with the replication origins of alphaherpesviruses; these origins are less complex and are centered around binding sites for a virus-encoded replication initiator protein, the OBP.Roseoloviruses each encode a homolog of the alphaherpesvirus OBP (14,16,23), which has no homolog in the cytomegaloviruses. The most extensively characterized alphaherpesvirus OBP, herpes simplex virus type 1 (HSV-1) OBP (OBP H1 ), binds as a dimer at each of two sites in its origins of replication (Box sites I and II in each ori S and two Box I sites in ori L ) (17).…”

mentioning

confidence: 99%

Sequence Requirements for Interaction of Human Herpesvirus 7 Origin Binding Protein with the Origin of Lytic Replication

Krug

Inoue

Pellett

2001

As do human herpesvirus 6 variants A and B (HHV-6A and -6B), HHV-7 encodes a homolog of the alphaherpesvirus origin binding protein (OBP), which binds at sites in the origin of lytic replication (oriLyt) to initiate DNA replication. In this study, we sought to characterize the interaction of the HHV-7 OBP (OBP H7 ) with its cognate sites in the 600-bp HHV-7 oriLyt. We expressed the carboxyl-terminal domain of OBP H7 and found that amino acids 484 to 787 of OBP H7 were sufficient for DNA binding activity by electrophoretic mobility shift analysis. OBP H7 has one high-affinity binding site (OBP-2) located on one flank of an AT-rich spacer element and a low-affinity site (OBP-1) on the other. This is in contrast to the HHV-6B OBP (OBP H6B ), which binds with similar affinity to its two cognate OBP sites in the HHV-6B oriLyt. The minimal recognition element of the OBP-2 site was mapped to a 14-bp sequence. The OBP H7 consensus recognition sequence of the 9-bp core, BRTYCWCCT (where B is a T, G, or C; R is a G or A; Y is a T or C; and W is a T or A), overlaps with the OBP H6B consensus YGWYCWCCY and establishes YCWCC as the roseolovirus OBP core recognition sequence. Heteroduplex analysis suggests that OBP H7 interacts along one face of the DNA helix, with the major groove, as do OBP H6B and herpes simplex virus type 1 OBP. Together, these results illustrate both conserved and divergent DNA binding properties between OBP H7 and OBP H6B . Human herpesvirus 7 (HHV-7) is a widely prevalent betaherpesvirus with an in vitro tropism for CD4ϩ T lymphocytes (reviewed in reference 5). HHV-7 is usually acquired during early childhood after HHV-6 infection and is likely transmitted via saliva (29). HHV-7 has been associated with febrile illnesses in children, neurological manifestations during primary infection, and clinical complications in organ transplant patients.The betaherpesvirus subfamily consists of the cytomegaloviruses and the roseoloviruses (HHV-7 and HHV-6 variants A and B [HHV-6A and HHV-6B]). Their genomes are genetically colinear, with origins of lytic replication (oriLyts) in analogous positions upstream from U41, the gene encoding the major DNA binding protein (1,7,11,23,27). However, sequence features of their oriLyt regions indicate substantial differences between cytomegaloviruses and roseoloviruses in their mechanisms for initiating viral replication. The minimal oriLyt regions of the cytomegaloviruses are long (Ͼ1.3-kb) complex structures consisting of multiple inverted and direct repeats, in addition to numerous transcription factor recognition sites that are believed to mediate activation of the replication origin (2,20,21,28). Unlike the cytomegaloviruses, oriLyts of HHV-6A and HHV-6B have features in common with the replication origins of alphaherpesviruses; these origins are less complex and are centered around binding sites for a virus-encoded replication initiator protein, the OBP.Roseoloviruses each encode a homolog of the alphaherpesvirus OBP (14,16,23), which has no homolog in the cytomegaloviru...