Fig. 4

Identification of amino-acids positions modulating the IN/H4 interaction. The interaction between the HIV-1 CTD and a pentapeptide derived from the H4K20me1 modified histone tail was predicted from docking simulations. The representation of the H4K20me1 pentapeptide (pink ball-and-stick model) docked into the HIV-1 IN CTD (gray surface) is shown in (a). The 228-235 and 253-257 loops are shown in yellow and cyan, respectively. Residues Y227, R231 and W235, represented in stick form, are highlighted in green. The model shows the K20me1 side chain pointing down into the V-shaped groove defined by loops 228–235 and 253–257. View of the docking model rotated 180° relative to panel A, using the same color scheme. Predicted hydrogen bonds and hydrophobic contacts are depicted by red and blue dashed lines, respectively. Residues interacting with the H4K20me1 pentapeptide are depicted by white sticks. Residues highlighted in green are those being mutated in this study. At the exception of W235, they all interact with the pentapeptide as well. Point mutations were introduced at residues potentially involved in H4 tail interaction recognition and their binding to the histone H4 peptide tail was analyzed using far dot blot experiments (b, see text for details). The binding measured with 5 pmol of enzyme is reported as the mean of three to ten independent experiments ± standard deviation. The p values were calculated by Student’s t-test and are represented as *p < 0.05 and **p < 0.005 to denote the probability of obtaining significant differences compared with the data obtained with the WT enzyme