Genome Although LLOV was isolated in
tissue culture, yet its genome has been determined in its entirety with exception of the
3' and
5' UTRs. The LLOV genome is probably approximately 19
kb long and contains seven
genes in the order
3'-UTR-
NP-
VP35-
VP40-
GP-
VP30-
VP24-
L-
5'-UTR. In contrast to
ebolaviruses and
Marburgviruses, which synthesize seven mRNAs to express the seven structural proteins, LLOV seems to produce only six
mRNAs, i.e. one mRNA (
VP24/
L) is thought to be
bicistronic. LLOV genomic
transcriptional termination sites are identical to those of
ebolavirus genomes but different from those of
Marburgvirus genomes. LLOV
transcriptional initiation sites are unique. The virus RdRp would partially uncoat the nucleocapsid and
transcribe the
genes into positive-stranded
mRNAs, which would then be
translated into structural and nonstructural
proteins. LLOV L would bind to a single
promoter located at the 3' end of the genome. Transcription would either terminate after a gene or continue to the next gene downstream. This means that genes close to the 3' end of the genome would be transcribed in the greatest abundance, whereas those toward the 5' end would be least likely to be transcribed. The gene order would therefore be a simple but effective form of transcriptional regulation. The most abundant protein produced would be the
nucleoprotein, whose
concentration in the cell would determine when L switches from gene transcription to genome replication. Replication would result in full-length, positive-stranded antigenomes that would in turn be transcribed into negative-stranded virus progeny genome copies. Newly synthesized structural proteins and genomes would self-assemble and accumulate near the inside of the
cell membrane. Virions would
bud off from the cell, gaining their envelopes from the cellular membrane they bud from. The mature progeny particles would then infect other cells to repeat the cycle. ==References==