Herpesvirus DNA-directed DNA polymerase (Pol)

Herpesvirus DNA-directed DNA polymerase is a fundamental enzyme required for the replication of the double-stranded DNA genomes of viruses within the Herpesviridae family, including Herpes Simplex Virus (HSV), Varicella-Zoster Virus (VZV), and Cytomegalovirus (CMV) [3, 5]. This enzyme belongs to the Family B DNA polymerases and typically operates as a complex comprising a catalytic subunit and a processivity factor that enhances the enzyme's ability to synthesize long DNA strands without dissociating [3, 5]. The catalytic subunit exhibits both 5'-3' polymerase activity for DNA synthesis and 3'-5' exonuclease activity for proofreading, which is vital for maintaining viral genetic stability [3, 7]. As an essential component of the viral lytic cycle, it serves as the primary target for the majority of approved anti-herpetic medications [1, 3]. Drugs such as acyclovir and ganciclovir act as prodrugs that, once activated by viral kinases, competitively inhibit the polymerase and induce premature chain termination of the nascent viral DNA [1, 2]. Other inhibitors, like foscarnet, bind directly to the pyrophosphate-binding site of the enzyme to block its activity [1, 6]. Despite the success of these therapies, the development of resistance through mutations in the polymerase gene is a major concern, especially during long-term treatment in immunocompromised individuals [3, 4].

Other names

Viral DNA polymeraseDNA-directed DNA polymerase catalytic subunitUL30UL54BALF5Herpesvirus DNA polymerase

The primary mechanism of action for drugs targeting this enzyme involves the use of nucleoside or nucleotide analogues that act as competitive inhibitors of the viral DNA polymerase and/or as DNA chain terminators after being incorporated into the growing viral DNA strand [1, 2, 3]. Additionally, pyrophosphate analogues like foscarnet directly inhibit the enzyme by binding to its pyrophosphate-binding site, preventing the release of pyrophosphate from deoxynucleoside triphosphates and halting DNA synthesis [1, 6].