Viral precursor protein P3 and its processed products perform discrete and essential functions in the poliovirus RNA replication complex.

The differential use of protein precursors and their products is a key strategy used during poliovirus replication. To characterize the role of protein precursors during replication, we examined the complementation profiles of mutants that inhibited 3D polymerase or 3C-RNA binding activity. We showed that 3D entered the replication complex in the form of its precursor, P3 (or 3CD), and was cleaved to release active 3D polymerase.

Sam68 enhances the cytoplasmic utilization of intron-containing RNA and is functionally regulated by the nuclear kinase Sik/BRK.

Cells normally restrict the nuclear export and expression of intron-containing mRNA. In many cell lines, this restriction can be overcome by inclusion of cis-acting elements, such as the Mason-Pfizer monkey virus constitutive transport element (CTE), in the RNA. In contrast, we observed that CTE-mediated expression from human immunodeficiency virus Gag-Pol reporters was very inefficient in 293 and 293T cells.