Figure 13

Model for the post-transcriptional regulation of gammaretroviral gag mRNA by NXF1 and SRp20. Translation of gammaretroviral Gag polyprotein requires recruitment of NXF1 to the gag mRNA. Recruitment of NXF1 might be direct, as it is with the MPMV CTE and appears to be with the γ-CTE located in pol, or indirect, via binding SRp20. (A) When NXF1 and SRp20 proteins are present at endogenous levels, direct binding of NXF1 to the γ-CTE in pol appears to be essential for Gag translation. (B) When NXF1 is overexpressed, some Gag protein is produced by gag alone, perhaps due to indirect NXF1 recruitment by SRp20. (C) When SRp20 is overexpressed, significant increase in Gag protein is observed with either gag alone or with gag-pol.