GST-Mo-MLV p12_M63I and other p12 orthologs associate with mitotic chromatin.

<p>(A) Representative silver stained gel (left) and immunoblot (right) showing binding of a panel of GST-p12 mutants to host proteins. 293T cells were transiently-transfected with expression constructs for GST-tagged Mo-MLV p12_WT (lane 1) and a panel of Mo-MLV p12 mutants: M63I (lane 2), G49R/E50K (lane 3), D25A/L-dom (carrying alanine substitutions of the PPPY motif as well as D25A, which disrupts clathrin binding, lane 4), p12 CTD only (lane 5) or GST-p12+<i>h</i>CBS (positive control, lane 6) for ~24 h before being treated overnight with nocodazole. GST-p12 protein complexes were precipitated from normalised cell lysates with glutathione-sepharose beads and analysed by SDS-PAGE followed by silver-staining or immunoblotting with anti-CLTC, anti-WWP2, anti-H2A, anti-H2B, anti-H3 and anti-H4 antibodies. Bands corresponding to core histones in the silver-stained gel are starred. (B) Infectivity of Mo-MLV VLPs carrying alterations in p12. HeLa cells were challenged with equivalent RT units of <i>LacZ</i>-encoding VLPs carrying Mo-MLV p12_WT, M63I, G49R/E50K or p12+<i>h</i>CBS +/- Mut14, and infectivity was measured 72 h post-infection by detection of beta-galactosidase activity in a chemiluminescent reporter assay. The data are plotted as percentage of WT VLP infectivity (mean ± SEM of >3 biological replicates). (C) An alignment of p12 sequences from selected gammaretroviruses. The CTD region is shaded pink. The S61 and M63 residues of Mo-MLV p12 are highlighted in red and equivalent residues at position 63 and 64 are boxed. CTD peptide sequences used in subsequent BLI assays (<a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1007117#ppat.1007117.g009" target="_blank">Fig 9</a>) are in bold. (D and E) Representative silver stained gel (top) and immunoblot (bottom) showing interaction of a panel of GST-tagged p12 orthologues (D) and GST-tagged FeLV_p12 mutants I52M and A53V (E) to chromatin associated proteins. GST-pull down assays were performed as in (A). (E) The amount of histone H2B pulled-down with GST-p12 was quantified for each sample by estimating median band intensity of immunoblots using a Li-cor Odyssey imaging system and plotted in the bar chart as mean ± SD of 3 technical replicates.