1,2,3,4-Tetrahydroisoquinolines as inhibitors of HIV-1 integrase and human LEDGF/p75 interaction.

Alkaloids are a class of organic compounds with a wide range of biological properties, including anti-HIV activity. The 1,2,3,4-tetrahydroisoquinoline is a ubiquitous structural motif of many alkaloids. Using a short and an efficient route for synthesis, a series of 1,2,3,4-tetrahydroisoquinolines/isoquinolines was developed.

L368F/V408F double mutant of IBD of LEDGF/p75 retains interaction with M178I mutant of HIV-1 integrase.

Lens-epithelium-derived-growth factor (LEDGF/p75) is an essential host protein for integration of HIV-1 DNA into host genome. Earlier alanine scanning mutational analysis has revealed that residues I365, D366 and F406 in the integrase binding domain (IBD) of p75 are critical for interaction with HIV-1 integrase (IN), while K364, V408 have intermediate effect and residues N367, L368, R405, K407 show wild type binding with IN. To gain insight into contribution of side chains of L368 and V408 that are adjacent to critical residues I365 and F406, respectively, site directed mutation of these residues to Ile/Leu, Met and Phe has been performed and characterized in this study.

Mechanistic insights into type III restriction enzymes.

Type III restriction-modification (R-M) enzymes need to interact with two separate unmethylated DNA sequences in indirectly repeated, head-to-head orientations for efficient cleavage to occur at a defined location next to only one of the two sites. However, cleavage of sites that are not in head-to-head orientation have been observed to occur under certain reaction conditions in vitro. ATP hydrolysis is required for the long-distance communication between the sites prior to cleavage.

Identification of host proteins associated with HIV-1 preintegration complexes isolated from infected CD4+ cells.

An integrated HIV-1 genomic DNA leads to an infected cell becoming either an active or a latent virus-producing cell. Upon appropriate activation, a latently infected cell can result in production of progeny viruses that spread the infection to uninfected cells. The host proteins influence several steps of HIV-1 infection including formation of the preintegration complex (PIC), a key nucleoprotein intermediate essential for integration of reverse transcribed viral DNA into the chromosome.

Quantitative analysis of HIV-1 preintegration complexes.

Retroviral replication proceeds through the formation of a provirus, an integrated DNA copy of the viral RNA genome. The linear cDNA product of reverse transcription is the integration substrate and two different integrase activities, 3' processing and DNA strand transfer, are required for provirus formation. Integrase nicks the cDNA ends adjacent to phylogenetically-conserved CA dinucleotides during 3' processing.

Chromatinized templates reveal the requirement for the LEDGF/p75 PWWP domain during HIV-1 integration in vitro.

Integration is an essential step in the retroviral lifecycle, and the lentiviral integrase binding protein lens epithelium-derived growth factor (LEDGF)/p75 plays a crucial role during human immunodeficiency virus type 1 (HIV-1) cDNA integration. In vitro, LEDGF/p75 stimulates HIV-1 integrase activity into naked target DNAs. Here, we demonstrate that this chromatin-associated protein also stimulates HIV-1 integration into reconstituted polynucleosome templates.

LEDGF/p75 functions downstream from preintegration complex formation to effect gene-specific HIV-1 integration.

LEDGF/p75 directly interacts with lentiviral integrase proteins and can modulate their enzymatic activities and chromosomal association. A novel genetic knockout model was established that allowed us for the first time to analyze HIV-1 integration in the absence of LEDGF/p75 protein. Supporting a crucial role for the cofactor in viral replication, HIV-1 vector integration and reporter gene expression were significantly reduced in LEDGF-null cells.

LEDGF/p75 interferes with the formation of synaptic nucleoprotein complexes that catalyze full-site HIV-1 DNA integration in vitro: implications for the mechanism of viral cDNA integration.

An integrase dimer can process and integrate a single HIV-1 DNA end in vitro, whereas a tetramer is required to integrate two ends. LEDGF/p75 can potently stimulate integrase activity, but its effects on half- versus full-site integration have not been investigated. Stimulation of half-site but inhibition of full-site integration is revealed here.

Exogenous AdoMet and its analogue sinefungin differentially influence DNA cleavage by R.EcoP15I--usefulness in SAGE.

While it has been demonstrated that AdoMet is required for DNA cleavage by Type III restriction enzymes, here we show that in the presence of exogenous AdoMet, the head-to-head oriented recognition sites are cleaved only on a supercoiled DNA. On a linear DNA, exogenous AdoMet strongly drives methylation while inhibiting cleavage reaction. Strikingly, AdoMet analogue sinefungin results in cleavage at all recognition sites irrespective of the topology of DNA.

Unidirectional translocation from recognition site and a necessary interaction with DNA end for cleavage by Type III restriction enzyme.

Type III restriction enzymes have been demonstrated to require two unmethylated asymmetric recognition sites oriented head-to-head to elicit double-strand break 25-27 bp downstream of one of the two sites. The proposed DNA cleavage mechanism involves ATP-dependent DNA translocation. The sequence context of the recognition site was suggested to influence the site of DNA cleavage by the enzyme.