Interaction of Initiation Factors and Capsid Protein with the Cap Structure of Chimaeric mRNAs Containing the 5′ Untranslated Regions of the RNAs of Semliki Forest Virus

Abstract

A considerable effort has been put into the understanding how Semliki Forest virus overrules the protein synthetic machinery of the host, promoting the translation of its own late 26S mRNAs while suppressing those of the host cell and its own genomic 42S RNA (van Steeg et al., 1981a; van Steeg et al., 1981b). Two major virus-specific RNAs are found in alphavirus-infected cells: the genomic 42S RNA and the subgenomic 26S RNA, comprising about one third of the 3′ part of the 42S RNA (Kaariainen and Soderlund, 1978). Both the 42S viral mRNA, which is utilized as an early mRNA for the synthesis of non structural proteins (Kaariainen and Soderlund, 1978; Wengler et al., 1979) and the subgenomic late 26S mRNA, which encodes the structural proteins later in infection (Kaariainen and Soderlund, 1978), are capped (Petterson et al., 1980; Wengler et al., 1979). Late in infection proteins are synthesized from 26S RNA in SFV-infected cells, despite the fact that 50% of the mRNA population is of cellular origin (van Steeg et al., 1981b; Tuomi et al., 1975). In an effort to explain how host shut off takes place, it has been suggested that viral mRNAs compete with cellular mRNAs for components of the translational apparatus of the host cell (Tuomi et al., 1975: Kozak, 1986; Schneider and Shenk, 1987).