Abstract
The matrix domain (MA) of the HIV-1 precursor Gag (PrGag) protein directs PrGag proteins to assembly sites at the plasma membrane by virtue of its affinity to the phospholipid, phosphatidylinositol-4,5-bisphosphate (PI(4,5)P(2)). MA also binds to RNA at a site that overlaps its PI(4,5)P(2) site, suggesting that RNA binding may protect MA from associating with inappropriate cellular membranes prior to PrGag delivery to the PM. Based on this, we have developed an assay in which small molecule competitors to MA-RNA binding can be characterized, with the assumption that such compounds might interfere with essential MA functions and help elucidate additional features of MA binding. Following this approach, we have identified four compounds, including three thiadiazolanes, that compete with RNA for MA binding. We also have identified MA residues involved in thiadiazolane binding and found that they overlap the MA PI(4,5)P(2) and RNA sites. Cell culture studies demonstrated that thiadiazolanes inhibit HIV-1 replication but are associated with significant levels of toxicity. Nevertheless, these observations provide new insights into MA binding and pave the way for the development of antivirals that target the HIV-1 matrix domain.
Highlights
The HIV-1 matrix protein (MA) binds both RNA and phospholipids
We have developed an assay in which small molecule competitors to matrix domain (MA)-RNA binding can be characterized, with the assumption that such compounds might interfere with essential MA functions and help elucidate additional features of MA binding
We recently analyzed HIV MA interactions with RNA ligands that previously were selected for their high affinities to MA [30], and we identified MA residues that are involved in RNA binding evident by nuclear magnetic resonance (NMR) chemical shift data [33]; interestingly, the RNA and PI[4,5]P2 binding sites overlap
Summary
The HIV-1 matrix protein (MA) binds both RNA and phospholipids. Results: Ligands that compete with RNA for binding to MA were identified and characterized. Cell culture studies demonstrated that thiadiazolanes inhibit HIV-1 replication but are associated with significant levels of toxicity These observations provide new insights into MA binding and pave the way for the development of antivirals that target the HIV-1 matrix domain. We recently analyzed HIV MA interactions with RNA ligands that previously were selected for their high affinities to MA [30], and we identified MA residues that are involved in RNA binding evident by NMR chemical shift data [33]; interestingly, the RNA and PI[4,5]P2 binding sites overlap These and results from other laboratories [34, 55] suggest that RNA may provide a chaperone function in preventing Gag proteins from binding to membranes until they reach PI[4,5]P2rich plasma membranes. Our efforts provide new insights into the nature of MA-RNA and MA-PI[4,5]P2 binding sites and open the door to the development of new classes of HIV antivirals
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