The reaction of the human immunodeficiency virus type 1 (HIV-1) nucleocapsid protein p7 (NCp7) with a variety of electrophilic agents was investigated by experimental measurements of Trp 37 fluorescence decay and compared with theoretical measures of reactivity based on density-functional theory in the context of the hard and soft acids and bases principle. Statistically significant correlations were found between rates of reaction and the ability of these agents to function as soft electrophiles. Notably, the molecular property that correlated strongest was the ratio of electronegativity to hardness, 2 /, a quantity related to the capacity of an electrophile to promote a soft (covalent) reaction. Electronic and steric determinants of the reaction were also probed by Fukui function and frontier-orbital overlap analysis in combination with protein-ligand docking methods. This analysis identified selective ligand docking regions within the conserved zinc finger domains that promoted reaction. The Cys 49 thiolate was found overall to be the NCp7 site most susceptible to electrophilic attack.

Agents that target the two highly conserved Zn fingers of the human immunodeficiency virus (HIV) nucleocapsid p7 (NCp7) protein are under development as antivirals. These agents covalently modify Zn-coordinating cysteine thiolates of the fingers, causing Zn ejection, loss of native protein structure and nucleic acid binding capacity, and disruption of virus replication. Concentrations of three antiviral agents that promoted in vitro Zn ejection from NCp7 and inhibited HIV replication did not impact the functions of cellular Zn finger proteins, including poly(ADP-ribose) polymerase and the Sp1 and GATA-1 transcription factors, nor did the compounds inhibit HeLa nuclear extract mediated transcription. Selectivity of interactions of these agents with NCp7 was supported by molecular modeling analysis which (1) identified a common saddle-shaped nucleophilic region on the surfaces of both NCp7 Zn fingers, (2) indicated a strong correspondence between computationally docked positions for the agents tested and overlap of frontier orbitals within the nucleophilic loci of the NCp7 Zn fingers, and (3) revealed selective steric exclusion of the agents from the core of the GATA-1 Zn finger. Further modeling analysis suggests that the thiolate of Cys49 in the carboxy-terminal finger is the site most susceptible to electrophilic attack. These data provide the first experimental evidence and rationale for antiviral agents that selectively target retroviral nucleocapsid protein Zn fingers.

Nucleocapsid p7 protein (NCp7) zinc finger domains of the human immunodeficiency virus type 1 (HIV-1) are being developed as antiviral targets due to their key roles in viral replication and their mutationally nonpermissive nature. On the basis of our experience with symmetrical disulfide benzamides (DIBAs; Rice et al. Science 1995, 270, 1194-1197), we synthesized and evaluated variants of these dimers, including sets of 4,4'- and 3,3'-disubstituted diphenyl sulfones and their monomeric benzisothiazolone derivatives (BITA). BITAs generally exhibited diminished antiviral potency when compared to their disulfide precursors. Novel, monomeric structures were created by linking haloalkanoyl groups to the benzamide ring through -NH-C(=O)- (amide) or -S-C(=O)- (thiolester) bridges. Amide-linked compounds generally lacked antiviral activity, while haloalkanoyl thiolesters and non-halogen-bearing analogues frequently exhibited acceptable antiviral potency, thus establishing thiolester benzamides per se as a new anti-HIV chemotype. Pyridinioalkanoyl thiolesters (PATEs) exhibited superior anti-HIV-1 activity with minimal cellular toxicity and appreciable water solubility. PATEs were shown to preferentially target the NCp7 Zn finger when tested against other molecular targets, thus identifying thiolester benzamides, and PATEs in particular, as novel NCp7 Zn finger inhibitors for in vivo studies.

Current antiestrogen therapy for breast cancer is limited by the mixed estrogenic and antiestrogenic activity of selective estrogen receptor modulators. Here we show that the function of zinc fingers in the estrogen receptor DNA-binding domain (DBD) is susceptible to chemical inhibition by electrophilic disulfide benzamide and benzisothiazolone derivatives, which selectively block binding of the estrogen receptor to its responsive element and subsequent transcription. These compounds also significantly inhibit estrogen-stimulated cell proliferation, markedly reduce tumor mass in nude mice bearing human MCF-7 breast cancer xenografts, and interfere with cell-cycle and apoptosis regulatory gene expression. Functional assays and computational analysis support a molecular mechanism whereby electrophilic agents preferentially disrupt the vulnerable C-terminal zinc finger, thus suppressing estrogen receptor-mediated breast carcinoma progression. Our results provide the proof of principle for a new strategy to inhibit breast cancer at the level of DNA binding, rather than the classical antagonism of estrogen binding.

A clinical case of linoleic acid deficiency has been investigated because of the unknown effect in an adult man. The patient had had all but 60 cm of his small intestine removed and was maintained solely by intravenous therapy for 100 days, without fat. At this stage there was no clinical evidence of malnutrition, but his serum phospholipids were found to contain 10% 5,8,11 eicosatrienoic acid and he developed a skin rash. A soybean fat emulsion containing 86 g/l of linoleic acid was given intravenously for 12 days, discontinued for 43 days and then resumed. During each period of fat administration (linoleic acid intake 22.8 g/day) the serum phospholipid content of eicosatrienoic acid fell and arachidonic acid rose. Simultaneously the serum triglycerides fell to normal, the proportions of the triglycerides carried by the lipoproteins (d < 1.006) rose to normal and the rash disappeared. A second case of linoleic acid deficiency, in this instance associated with severe malnutrition, was investigated and here also a high level of plasma triglycerides was mostly associated with lipoproteins with d < 1.006. In an attempt to estimate his minimal daily requirements, feeding 7.5 g/day of linoleic acid in this form did not eliminate the eicosatrienoic acid, but instead allowed a small increase. It is concluded that adult man requires at least 7.5 g/day of linoleic acid and that the proportion of the triglycerides carried by the very low density lipoproteins is lowered in the absence of linoleic acid.

SUMMARYHepatitis C virus (HCV) infects more than 3% of the world's population, leading to an increased risk of cirrhosis and hepatocellular carcinoma. The current standard of care, a combination of pegylated interferon alfa and ribavirin, is poorly tolerated and often ineffective against the most prevalent genotype of the virus, genotype 1. The very recent approval of boceprevir and telaprevir, two HCV protease inhibitors, promises to significantly improve treatment options and outcomes. In addition to the viral protease NS3 and the viral polymerase NS5B, direct-acting antivirals are now in development against NS5A. A multifunctional phosphoprotein, NS5A is essential to HCV genome replication, but has no known enzymatic function. Here we report how the design of small-molecule inhibitors against NS5A has evolved from promising monomers to highly potent dimeric compounds effective against many HCV genotypes. We also highlight recent clinical data and how the inhibitors may bind to NS5A, itself capable of forming dimers. HEPATITIS C VIRUS (HCV): AN INTERNATIONAL HEALTH CONCERNHepatitis C virus (HCV) infects approximately 170 million individuals, with an estimated 2.3-4.7 million new infections each year (1). The primary mode of transmission of HCV is via exposure to infected blood, including transfusions from infected donors, and through injection drug use. It is estimated that 15-30% of all HCV infections will spontaneously clear, but the remaining 70-85% of infections will develop into chronic hepatitis (2, 3). Chronic infections can subsequently lead to steatosis, cirrhosis and hepatocellular carcinoma (4). Among all recognized positive-strand RNA viruses, the ability to establish a chronic infection is exclusive to HCV (5), although how the virus mediates persistence remains unknown.Current treatment options for HCV are relatively poor. The standard of care is often a grueling 48-week combination of pegylated interferon alfa (IFN-α) and the nucleoside analogue ribavirin. Effective clearance of the virus is achieved in less than 50% of genotype

A boronic acid moiety was found to be a critical pharmacophore for enhanced in vitro potency against wild-type hepatitis C replicons and known clinical polymorphic and resistant HCV mutant replicons. The synthesis, optimization, and structure-activity relationships associated with inhibition of HCV replication in a subgenomic replication system for a series of non-nucleoside boron-containing HCV RNA-dependent RNA polymerase (NS5B) inhibitors are described. A summary of the discovery of 3 (GSK5852), a molecule which entered clinical trials in subjects infected with HCV in 2011, is included.

Analysis of CCR5 variants in human immunodeficiency virus, type 1 (HIV-1), high risk cohorts led to the identification of multiple single amino acid substitutions in the amino-terminal third of the HIV-1 co-receptor CCR5 suggesting the possibility of protective and permissive genotypes; unfortunately, the low frequency of these mutations did not led to correlation with function. Therefore, we used analytical methods to assess the functional and structural significance of six of these variant receptors in vitro. These studies showed three categories of effects on CCR5 function. 1) Mutations in the first extracellular domain of CCR5 severely reduce specific ligand binding and chemokine-induced chemotaxis. 2) An extracellular domain variant, A29S, when co-expressed with CD4, supported HIV-1 infection whereas the others do not.3) The transmembrane region variants of CCR5 support monotropic HIV-1 infection that is blocked by addition of some receptor agonists. Mutations in the first and second transmembrane domains increase RANTES (regulated on activation normal T-cell expressed) binding affinity but did not affect MIP1␤ binding affinity presumably based on differences in ligand-receptor interaction sites. Furthermore, the CCR5 transmembrane mutants do not respond to RAN-TES with the classical bell-shaped chemotactic response curve, suggesting that they are resistant to RANTESinduced desensitization. These data demonstrate that single amino acid changes in the extracellular domains of CCR5 can have profound effects on both HIV-1 coreceptor and specific ligand-induced functions, whereas mutations in the transmembrane domain only affect the response to chemokine ligands.