Anti-HIV Agents That Selectively Target Retroviral Nucleocapsid Protein Zinc Fingers without Affecting Cellular Zinc Finger Proteins

Abstract

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.

Inactivation of HIV-1 Nucleocapsid Protein P7 by Pyridinioalkanoyl Thioesters

“…Our results provide direct evidence of this differential zinc ejection. The greater reactivity of the carboxyl-terminal zinc finger toward attack by a variety of electrophiles has been attributed to a combination of steric factors and differences in nucleophilicity of the cysteines (22)(23)(24). Molecular modeling studies based on density-functional theory suggested that the thiolate of Cys 49 is the most electron rich and the most reactive toward highly polarizable electrophiles (23).…”

“…Molecular modeling studies based on density-functional theory suggested that the thiolate of Cys 49 is the most electron rich and the most reactive toward highly polarizable electrophiles (23). Molecular modeling studies show that the reactive sites of the carboxyl-terminal zinc finger lie in a more contiguous reactive surface compared with the amino-terminal finger (24). Docking of some antiviral agents, 2,2Ј-dithiobis(benzamide) disulfides-1 in particular, revealed that the structure of the carboxyl-terminal finger allows a significantly closer approach of the ligands to the cysteine thiolates, compared with the amino-terminal finger (24).…”

Potential inhibition of HIV-1 encapsidation by oligoribonucleotide–dendrimer nanoparticle complexes

“…[1][2][3][4] This process involves interaction between the gag nucleocapsid protein p7 (NCp7) and a region of the HIV genome known as the packaging signal (Ψ). This interaction is an attractive target for antiviral therapy because the secondary structures of Ψ and nucleocapsid are highly conserved among retroviruses [5][6][7][8][9] and mutations in NCp7 result in totally defective virions. [10][11][12] This suggests that drug resistance to "packaging inhibitors" is less likely to develop.…”

Single DNA molecule stretching measures the activity of chemicals that target the HIV-1 nucleocapsid protein

“…They can target the residues that coordinate the zinc ions, to a greater (Cys-49, Cys-36) or lesser (Cys-39) extent (25). Several studies proved that some compounds can have high selectivity for the CCHC zinc finger-type found only in retroviruses and a very few cellular proteins, such as poly(ADP-ribose) polymerase (26). However, the zinc ejector agents are still avoided because of their potential cytotoxicity at high concentrations.…”