Structure-based amelioration of PXR transactivation in a novel series of macrocyclic allosteric inhibitors of HIV-1 integrase

Previous studies have identified a series of imidazo[1,2-a]pyridine (IZP) derivatives as potent allosteric inhibitors of HIV-1 integrase (ALLINIs) and virus infection in cell culture. However, IZPs were also found to be relatively potent activators of the pregnane-X receptor (PXR), raising the specter of induction of CYP-mediated drug disposition pathways. In an attempt to modify PXR activity without affecting anti-HIV-1 activity, rational structure-based design and modeling approaches were used. An X-ray cocrystal structure of (S,S)-1 in the PXR ligand binding domain (LBD) allowed an examination of the potential of rational structural modifications designed to abrogate PXR. The introduction of bulky basic amines at the C-8 position provided macrocyclic IZP derivatives that displayed potent HIV-1 inhibitory activity in cell culture with no detectable PXR transactivation at the highest concentration tested.     

Keratan sulfate and related murine glycosylation can suppress murine cartilage damage in vitro and in vivo

Nucleolar spindle associated protein (NuSAP) is a microtubule-stabilizing protein that localizes to chromosome arms and chromosome-proximal microtubules during mitosis and to the nucleus, with enrichment in the nucleoli, during interphase. The critical function of NuSAP is underscored by the finding that its depletion in HeLa cells results in various mitotic defects. Moreover, NuSAP is found overexpressed in multiple cancers and its expression levels often correlate with the aggressiveness of cancer. Due to its localization on chromosome arms and combination of microtubule-stabilizing and DNA-binding properties, NuSAP takes a special place within the extensive group of spindle assembly factors. In this study, we identify a SAP-like domain that shows DNA binding in vitro with a preference for dsDNA. Deletion of the SAP-like domain abolishes chromosome arm binding of NuSAP during mitosis, but is not sufficient to abrogate its chromosome-proximal localization after anaphase onset. Fluorescence recovery after photobleaching experiments revealed the highly dynamic nature of this NuSAP-chromatin interaction during mitosis. In interphase cells, NuSAP also interacts with chromatin through its SAP-like domain, as evident from its enrichment on dense chromatin regions and intranuclear mobility, measured by fluorescence correlation spectroscopy.The obtained results are in agreement with a model where NuSAP dynamically stabilizes newly formed microtubules on mitotic chromosomes to enhance chromosome positioning without immobilizing these microtubules. Interphase NuSAP-chromatin interaction suggests additional functions for NuSAP, as recently identified for other nuclear spindle assembly factors with a role in gene expression or DNA damage response.     

Role of the PWWP domain of lens epithelium-derived growth factor (LEDGF)/p75 cofactor in lentiviral integration targeting

LEDGF/p75 is a chromatin-interacting, cellular cofactor of HIV integrase that dictates lentiviral integration site preference. In this study we determined the role of the PWWP domain of LEDGF/p75 in tethering and targeting of the lentiviral pre-integration complex, employing potent knockdown cell lines allowing analysis in the absence of endogenous LEDGF/p75. Deletion of the PWWP domain resulted in a diffuse subnuclear distribution pattern, loss of interaction with condensed chromatin, and failure to rescue proviral integration, integration site distribution, and productive virus replication. Substitution of the PWWP domain of LEDGF/p75 with that of hepatoma-derived growth factor or HDGF-related protein-2 rescued viral replication and lentiviral integration site distribution in LEDGF/p75-depleted cells. Replacing all chromatin binding elements of LEDGF/p75 with full-length hepatoma-derived growth factor resulted in more integration in genes combined with a preference for CpG islands. In addition, we showed that any PWWP domain targets SMYD1-like sequences. Analysis of integration preferences of lentiviral vectors for epigenetic marks indicates that the PWWP domain is critical for interactions specifying the relationship of integration sites to regions enriched in specific histone post-translational modifications.     

Identification of small peptides inhibiting the integrase‐LEDGF/p75 interaction through targeting the cellular co‐factor

The integration of the viral DNA into the host genome is one of the essential steps in the HIV replication cycle. This process is mediated by the viral enzyme integrase (IN) and lens epithelium‐derived growth factor (LEDGF/p75). LEDGF/p75 has been identified as a crucial cellular co‐factor of integration that acts by tethering IN to the cellular chromatin. Recently, circular peptides were identified that bind to the C‐terminal domain of IN and disrupt the interaction with LEDGF/p75. Starting from the circular peptides, we identified a short peptidic sequence able to inhibit the LEDGF/p75‐IN interaction at low μM concentration through its binding to the IN binding site of LEDGF/p75. This discovery can lead to the synthesis of peptidomimetics with high anti‐HIV activity targeting the cellular co‐factor LEDGF/p75 and not the viral protein IN. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.     

Fragment hopping approach directed at design of HIV IN-LEDGF/p75 interaction inhibitors

We recently identified a series of indole derivatives as active inhibitors of IN-LEDGF/p75 interaction through structure-based pharmacophore models generated from the crystal structure of dimeric catalytic core domain (CCD) of HIV-1 IN in complex with the LEDGF integrase binding domain (IBD). In this paper we used the fragment hopping approach to design small molecules able to prevent the IN-LEDGF/p75 interaction. By means of the proposed approach, we designed novel non-peptidyl compounds that mimic the biological function of some IBD residues and in particular the LEDGF hot spot residues Ile365 and Asp366. The biological results confirmed the importance of several structural requirements for the inhibitory effects of this class of compounds.     

Development of hybrid viral vectors for gene therapy

Adenoviral, retroviral/lentiviral, adeno-associated viral, and herpesviral vectors are the major viral vectors used in gene therapy. Compared with non-viral methods, viruses are highly-evolved, natural delivery agents for genetic materials. Despite their remarkable transduction efficiency, both clinical trials and laboratory experiments have suggested that viral vectors have inherent shortcomings for gene therapy, including limited loading capacity, immunogenicity, genotoxicity, and failure to support long-term adequate transgenic expression. One of the key issues in viral gene therapy is the state of the delivered genetic material in transduced cells. To address genotoxicity and improve the therapeutic transgene expression profile, construction of hybrid vectors have recently been developed. By adding new abilities or replacing certain undesirable elements, novel hybrid viral vectors are expected to outperform their conventional counterparts with improved safety and enhanced therapeutic efficacy. This review provides a comprehensive summary of current achievements in hybrid viral vector development and their impact on the field of gene therapy.