FIG. 9.

Involvement of RNA in the interaction of fibrillarin and N. (A) The GST-fibrillarin (Fibn) fusion protein was expressed in E. coli and subjected to a GST pull-down assay in the presence of 100 μg of RNase A/ml. The GST-fibrillarin-bound Sepharose beads were incubated with the [³⁵S]methionine-labeled N protein prepared from virus-infected cells. The beads were washed, and the bound proteins were resolved by SDS-PAGE followed by autoradiography. Nucleolin as a GST fusion protein (GST-Ncl) was included as a control. N-IP, the immunoprecipitated N protein as a molecular mass marker. (B) GST pull-down assay using the phosphorylated N protein radiolabeled in vivo with inorganic [³²P]orthophosphate upon virus infection. GST fusion proteins were subjected to a GST pull-down assay using the ³²P-labeled N protein as the probe prepared from cells infected by PRRSV.