Complex interactions of HIV-1 nucleocapsid protein with oligonucleotides

The HIV-1 nucleocapsid (NC) protein is a small, basic protein containing two retroviral zinc fingers. It is a highly active nucleic acid chaperone; because of this activity, it plays a crucial role in virus replication as a cofactor during reverse transcription, and is probably important in other steps of the replication cycle as well. We previously reported that NC binds with high-affinity to the repeating sequence d(TG)(n). We have now analyzed the interaction between NC and d(TG)(4) in considerable detail, using surface plasmon resonance (SPR), tryptophan fluorescence quenching (TFQ), fluorescence anisotropy (FA), isothermal titration calorimetry (ITC) and electrospray ionization Fourier transform mass spectrometry (ESI-FTMS). Our results show that the interactions between these two molecules are surprisngly complex: while the K(d) for binding of a single d(TG)(4) molecule to NC is only ∼5 nM in 150 mM NaCl, a single NC molecule is capable of interacting with more than one d(TG)(4) molecule, and conversely, more than one NC molecule can bind to a single d(TG)(4) molecule. The strengths of these additional binding reactions are quantitated. The implications of this multivalency for the functions of NC in virus replication are discussed

Complex interactions of HIV-1 nucleocapsid protein with oligonucleotides-0

<p><b>Copyright information:</b></p><p>Taken from "Complex interactions of HIV-1 nucleocapsid protein with oligonucleotides"</p><p>Nucleic Acids Research 2006;34(3):1082-1082.</p><p>Published online 13 Feb 2006</p><p>PMCID:PMC1369284.</p><p>© The Author 2006. Published by Oxford University Press. All rights reserved</p

Small molecule inhibitors of HDM2 ubiquitin ligase activity stabilize and activate p53 in cells

The p53 tumor suppressor protein is regulated by its interaction with Ill which serves as a ubiquitin ligase (E3) to target p53 for degradation. We have identified a family of small molecules (HL198) that inhibits HDM2's E3 activity. These compounds show some specificity for HDM2 in vitro, although at higher concentrations effects on unrelated RING and HECT domain E3s are detectable, which could be due, at least in part, to effects on E2-ubiquitin thiol-ester levels. In cells, the compounds allow the stabilization of p53 and HDM2 and activation of p53-dependent transcription and apoptosis, although other p53-independent toxicity was also observed