VIRION
Filamentous 790 nm long for Marburg virus and 970 nm long for Ebolavirus. Diameter is about 80nm.
GENOME
Negative-stranded RNA linear genome, about 18-19 kb in size. Encodes for seven proteins.
GENE EXPRESSION
The viral RNA dependent RNA polymerase binds the encapsidated genome at the leader region, then sequentially transcribes each genes by recognizing start and stop signals flanking viral genes. mRNAs are capped and polyadenylated by the L protein during synthesis.
In Ebolavirus, the primary product of the unedited transcript of GP gene yields a smaller non-structural glycoprotein sGP which is efficiently secreted from infected cells. RNA editing allows expression of full-length GP.
ENZYMES
- RNA-dependent RNA polymerase [L]
- Mononega-type capping
- RNA TPase, GTase, N7 Mtase, 2'O Mtase [L]
REPLICATION
CYTOPLASMIC
- Attachment to host receptors through GP glycoprotein mediates is endocytosed into vesicles in the host cell by apoptotic mimicry
- Fusion of virus membrane with the vesicle membrane; ribonucleocapsid is released into the cytoplasm.
- Sequential transcription, viral mRNAs are capped and polyadenylated by polymerase stuttering in the cytoplasm.
- Replication presumably starts when enough nucleoprotein is present to encapsidate neo-synthetized antigenomes and genomes.
- The ribonucleocapsid interacts with the matrix protein under the plasma membrane, buds via the host ESCRT complexes from the plasma membrane, releasing the virion.
