S-nitrosylation of viral proteins: Molecular bases for antiviral effect ofnitric oxide

Nitric oxide (NO) is considered an important signaling molecule implied in various different physiological processes, including nervous transmission, vascular regulation, and immune defence, as well as the pathogenesis of sev eral diseases. NO reportedly also has an antiviral effect on several DNA an d RNA virus families. The NO-mediated S-nitrosylation of viral and host (ma cro)molecules appears to be an intriguing general mechanism for the control of the virus life cycle. In this respect, NO is able to nitrosylate cystei ne-containing enzymes (e.g., proteases, reverse transcriptase, and ribonucl eotide reductase). Moreover, zinc-fingers and related domains present in en zymes (e.g,, HIV-1-encoded integrase or herpes simplex virus type-1 heterot rimeric helicase-primase complex) or nucleocapsid proteins may be considere d as NO targets. Also, NO may regulate both host (e.g., nuclear factor-kapp a B) and viral-encoded (e.g,, HIV-1 tat protein or Epstein-Barr virus Zta) transcriptional factors that are involved in virus replication. Finally, NO -mediated S-nitrosylation of cysteine-containing glycoproteins and hemagglu tinin may also occur. Here, NO targets are summarised, and the molecular ba ses for the antiviral effect of NO are discussed.