The Labex Dynamo
2018 Mouhand et al.
Modulation of the HIV nucleocapsid dynamics finely tunes its RNA-binding properties during virion genesis. Nucleic Acids Res, 46 (2018).
Mouhand et al., 2018
During HIV-1 assembly and budding, Gag protein, in particular the C-terminal domain containing the nu- cleocapsid domain (NCd), p1 and p6, is the site of numerous interactions with viral and cellular factors. Most in vitro studies of Gag have used constructs lacking p1 and p6. Here, using NMR spectroscopy, we show that the p1–p6 region of Gag (NCp15) is largely disordered, but interacts transiently with the NCd. These interactions modify the dynamic prop- erties of the NCd. Indeed, using isothermal titration calorimetry (ITC), we have measured a higher en- tropic penalty to RNA-binding for the NCd precursor, NCp15, than for the mature form, NCp7, which lacks p1 and p6. We propose that during assembly and budding of virions, concomitant with Gag oligomer- ization, transient interactions between NCd and p1– p6 become salient and responsible for (i) a higher level of structuration of p6, which favours recruit- ment of budding partners; and (ii) a higher entropic penalty to RNA-binding at specific sites that favours non-specific binding of NCd at multiple sites on the genomic RNA (gRNA). The contributions of p6 and p1 are sequentially removed via proteolysis during Gag maturation such that the RNA-binding specificity of the mature protein is governed by the properties of NCd.
Publish on : 08/04/2019