Synthesis And Processing Of GAG, GAGPOL Polyproteins Evidence suggests that the RNA molecules used for the synthesis of Gag and Gag-Pro-Pol are not the same molecules that are packaged into virions. Gag proteins do not appear to aggregate around and capture the RNA contained in the polyribosome from which they emerged, but rather bind to and ultimately encapsidate free transcripts elsewhere. During the replication of retroviruses, large numbers of Gag molecules must be generated to serve as precursors to the structural proteins of the virions. Retroviruses have developed a mechanism that permits expression of the Gag protein at high levels relative to the protein sequences encoded in the pro and pol genes, while retaining coregulated expression. This linkage results from the use of the same initiation codon in the same mRNA to express the gag, pro, and pol genes. Translation of this RNA leads occasionally to synthesis of a fusion protein that is usually called the Gag-Pol precursor but is now more appropriately called the Gag-Pro-Pol precursor GENE ONTOLOGYGO:0019082 ISBN0-87969-571-4 Reactome Database ID Release 43174495 Reactome, http://www.reactome.org ReactomeREACT_115860 Synthesis and organization of GAG, GAGPOL polyproteins Membrane binding and targetting of GAG proteins PathwayStep3607 PathwayStep3608 Synthesis of GAG polyprotein