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English: Replication cycle of L-A helper and M28 killer viruses in S. cerevisiae. The L-A replication cycle starts in vivo, with the transcription of L-A dsRNA into L-A (+) strands, via the transcriptase activity of the Gag-Pol fusion protein. After extrusion into the cytoplasm, the majority of L-A (+) strands are translated into the capsid protein, Gag (grey dot), while only 1–2% are converted into a Gag-Pol fusion protein (green-grey dot) by a −1 ribosomal frameshift event. Viral L-A (+) strands further interact with Gag-Pol, which triggers L-A particle assembly and encapsidation [39]. The protein composition of newly assembled ScV-L-A particles, each of them containing just a single L-A (+) strand, is identical to that of mature virions. In the final step, an L-A (−) strand is synthesized by the replicase activity of Pol, leading to a complete dsRNA genome within each virion. Replication of ScV-M is analogous to that of ScV-L-A. After in vivo M (+) strand synthesis and subsequent extrusion into the cytoplasm, M (+) strands are either translated into the unprocessed K28 toxin precursor or bound by Gag-Pol for subsequent encapsidation into virus particles. ScV-M replication finally finishes with the synthesis of an M (−) strand. Compared to L-A virions, two M-dsRNA copies can be present in a single M virion at the same time, due to their smaller genome size.