[Show abstract][Hide abstract] ABSTRACT: Here we report recovery of infectious Marburg virus (MARV) from a full-length cDNA clone. Compared to the wild-type virus,
recombinant MARV showed no difference in terms of morphology of virus particles, intracellular distribution in infected cells,
and growth kinetics. The nucleocapsid protein VP30 of MARV and Ebola virus (EBOV) contains a Zn-binding motif which is important
for the function of VP30 as a transcriptional activator in EBOV, whereas its role for MARV is unclear. It has been reported
previously that MARV VP30 is able to support transcription in an EBOV-specific minigenome system. When the Zn-binding motif
was destroyed, MARV VP30 was shown to be inactive in the EBOV system. While it was not possible to rescue recombinant MARV
when the VP30 plasmid was omitted from transfection, MARV VP30 with a destroyed Zn-binding motif and EBOV VP30 were able to
mediate virus recovery. In contrast, rescue of recombinant EBOV was not supported by EBOV VP30 containing a mutated Zn-binding
Full-text · Article · Feb 2006 · Journal of Virology
[Show abstract][Hide abstract] ABSTRACT: In this work we investigated the cis-acting signals involved in replication of Ebola virus (EBOV) genomic RNA. A set of mingenomes with mutant 3' ends were generated and used in a reconstituted replication and transcription system. Our results suggest that the EBOV genomic replication promoter is bipartite, consisting of a first element located within the leader region of the genome and a second, downstream element separated by a spacer region. While proper spacing of the two promoter elements is a prerequisite for replication, the nucleotide sequence of the spacer is not important. Replication activity was only observed when six or a multiple of six nucleotides were deleted or inserted, while all other changes in length abolished replication completely. These data indicate that the EBOV replication promoter obeys the rule of six, although the genome length is not divisible by six. The second promoter element is located in the 3' nontranslated region of the first gene and consists of eight UN5 hexamer repeats, where N is any nucleotide. However, three consecutive hexamers, which could be located anywhere within the promoter element, were sufficient to support replication as long as the hexameric phase was preserved. By using chemical modification assays, we could demonstrate that nucleotides 5 to 44 of the EBOV leader are involved in the formation of a stable secondary structure. Formation of the RNA stem-loop occurred independently of the presence of the trailer, indicating that a panhandle structure is not formed between the 3' and 5' ends.
Full-text · Article · Sep 2005 · Journal of Virology
[Show abstract][Hide abstract] ABSTRACT: The nucleocapsid protein VP30 of Ebola virus (EBOV), a member of the Filovirus family, is known to act as a transcription activator. By using a reconstituted minigenome system, the role of VP30 during
transcription was investigated. We could show that VP30-mediated transcription activation is dependent on formation of a stem-loop
structure at the first gene start site. Destruction of this secondary structure led to VP30-independent transcription. Analysis
of the transcription products of bicistronic minigenomes with and without the ability to form the secondary structure at the
first transcription start signal revealed that transcription initiation at the first gene start site is a prerequisite for
transcription of the second gene, independent of the presence of VP30. When the transcription start signal of the second gene
was exchanged with the transcription start signal of the first gene, transcription of the second gene also was regulated by
VP30, indicating that the stem-loop structure of the first transcription start site acts autonomously and independently of
its localization on the RNA genome. Our results suggest that VP30 regulates a very early step of EBOV transcription, most
likely by inhibiting pausing of the transcription complex at the RNA structure of the first transcription start site.
Full-text · Article · Oct 2002 · Journal of Virology
[Show abstract][Hide abstract] ABSTRACT: To study the mechanisms underlying the high pathogenicity of Ebola virus, we have established a system that allows the recovery
of infectious virus from cloned cDNA and thus permits genetic manipulation. We created a mutant in which the editing site
of the gene encoding envelope glycoprotein (GP) was eliminated. This mutant no longer expressed the nonstructural glycoprotein
sGP. Synthesis of GP increased, but most of it accumulated in the endoplasmic reticulum as immature precursor. The mutant
was significantly more cytotoxic than wild-type virus, indicating that cytotoxicity caused by GP is down-regulated by the
virus through transcriptional RNA editing and expression of sGP.
[Show abstract][Hide abstract] ABSTRACT: The members of the family Filoviridae, Marburg virus (MBGV) and Ebola virus (EBOV), are very similar in terms of morphology, genome organization, and protein composition. To compare the replication and transcription strategies of both viruses, an artificial replication system based on the vaccinia virus T7 expression system was established for EBOV. Specific transcription and replication of an artificial monocistronic minireplicon was demonstrated by reporter gene expression and detection of the transcribed and replicated RNA species. As it was shown previously for MBGV, three of the four EBOV nucleocapsid proteins, NP, VP35, and L, were essential and sufficient for replication. In contrast to MBGV, EBOV-specific transcription was dependent on the presence of the fourth nucleocapsid protein, VP30. When EBOV VP30 was replaced by MBGV VP30, EBOV-specific transcription was observed but with lower efficiency. Exchange of NP, VP35, and L between the two replication systems did not lead to detectable reporter gene expression. It was further observed that neither MBGV nor EBOV were able to replicate the heterologous minigenomes. A chimeric minigenome, however, containing the EBOV leader and the MBGV trailer was encapsidated, replicated, transcribed, and packaged by both viruses.
Preview · Article · Apr 1999 · Journal of Virology