Multiple roles of the non-structural protein 3 (nsP3) alphavirus unique domain (AUD) during Chikungunya virus genome replication and transcription - Fig 1

(A) Schematic of the domain structure of the alphavirus nsP3 protein. (B) Surface representation of the Sindbis virus nsP3 AUD structure (PDB ID code 4GUA) [14] (residues 161–320), including the 40 amino acid flexible linker between the macrodomain and the AUD. The locations of the mutated residues in nsP3 are highlighted in colour with their designation alongside in text of the same colour. The two images show opposite faces of the structure, rotated 180o along the vertical axis. (C) Structure of CHIKV-D-Luc-SGR. This replicon was derived from the CHIKV ECSA strain LR2006 OPY1 isolate [15,16] and is described in [17]. Renilla luciferase (RLuc) is expressed as an internal fusion with nsP3 and thus is produced following translation of the input RNA. RLuc activity is therefore an indirect measure of both input translation and subsequent genome replication. Firefly luciferase (FLuc) is expressed from the subgenomic promoter (sg-prom) and thus is only produced after genome replication has occurred (synthesis of negative strand RNA that subsequently templates the production of both full-length genomic and sgRNA).