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FIG. 7. Summary model of µNS associations with other components in viral factories. (A) Bar diagram of µNS primary sequences (residues 1 to 721) indicating known features and regions shown to be required for protein associations. It remains to be demonstrated that µNS(41-721) and µNSC are equivalent. (B) Cartoon depicting the factory of a reovirus strain, such as T1L, whose µ2 protein recruits µNS to microtubules (MT) (8, 40). Ribosomes are excluded from the factories (42, 45), so protein synthesis must occur in surrounding regions of the cytoplasm. Core surface proteins ${lambda}$ 1, ${lambda}$ 2, and ${sigma}$ 2 are recruited to the factory through association with µNS (this study). The single-stranded RNA-binding protein ${sigma}$ NS is also recruited to the factory through association with µNS (4, 35). Core assembly, including the 10 genomic RNA segments and polymerase ${lambda}$ 3 which are not shown here, is proposed to occur within the factory but might also occur in surrounding regions of the cytoplasm as also shown in the cartoon. Cores assembled in the cytoplasm may then be recruited to the factory through association with µNS (this study). New plus-strand RNA transcripts produced by µNS-associated cores (36, 37) within the factory may be largely retained there, possibly by binding to ${sigma}$ NS (a), which may promote their assembly into progeny particles (sponge model). Some newly produced viral transcripts, however, must be released into the surrounding cytoplasm (b) to promote ongoing viral protein synthesis. The precise role of µNSC remains unclear and is therefore not shown. The mechanism of outer capsid assembly is also unclear and therefore not shown. Although the various protein associations are shown as direct interactions, there may be unidentified intermediaries or promoting agents in one or more cases.

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