Structural polyprotein

UniProtKB accession:  Q4QXJ7

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UniProtKB description:  Forms an icosahedral capsid with a T=4 symmetry composed of 240 copies of the capsid protein surrounded by a lipid membrane through which penetrate 80 spikes composed of trimers of E1-E2 heterodimers (By similarity). The capsid protein binds to the viral RNA genome at a site adjacent to a ribosome binding site for viral genome translation following genome release (By similarity). Possesses a protease activity that results in its autocatalytic cleavage from the nascent structural protein (By similarity). Following its self-cleavage, the capsid protein transiently associates with ribosomes, and within several minutes the protein binds to viral RNA and rapidly assembles into icosahedric core particles (By similarity). The resulting nucleocapsid eventually associates with the cytoplasmic domain of the spike glycoprotein E2 at the cell membrane, leading to budding and formation of mature virions (By similarity). In case of infection, new virions attach to target cells and after clathrin-mediated endocytosis their membrane fuses with the host endosomal membrane (By similarity). This leads to the release of the nucleocapsid into the cytoplasm, followed by an uncoating event necessary for the genomic RNA to become accessible (By similarity). The uncoating might be triggered by the interaction of capsid proteins with ribosomes (By similarity). Binding of ribosomes would release the genomic RNA since the same region is genomic RNA-binding and ribosome-binding (By similarity). Specifically inhibits interleukin-1 receptor-associated kinase 1/IRAK1-dependent signaling during viral entry, representing a means by which the alphaviruses may evade innate immune detection and activation prior to viral gene expression (By similarity). Inhibits host transcription (By similarity). Forms a tetrameric complex with XPO1/CRM1 and the nuclear import receptor importin (By similarity). This complex blocks the central channel of host nuclear pores thereby inhibiting the receptor-mediated nuclear transport and thus the host mRNA and rRNA transcription (By similarity). The inhibition of transcription is linked to a cytopathic effect on the host cell (By similarity).