Vaccinia virus thymidine kinase (VVTK) (VVTK)

Vaccinia virus thymidine kinase (VVTK), encoded by the J2R gene, is a critical enzyme in the pyrimidine salvage pathway of the vaccinia virus [UniProt P03902]. It facilitates viral DNA replication by phosphorylating thymidine into thymidine monophosphate (dTMP), a process particularly vital for the virus when infecting non-dividing cells with limited nucleotide pools [PubMed: 2825438]. VVTK is a significant pharmacological target; it selectively phosphorylates various nucleoside analogs, such as idoxuridine and trifluridine, converting them into active metabolites that inhibit viral DNA polymerase [DrugBank]. In modern biotechnology, VVTK is frequently utilized in the development of oncolytic viruses, where the J2R gene is deleted to ensure that viral replication is restricted to cancer cells that overexpress cellular thymidine kinase [PubMed: 21964414]. This enzyme also serves as a reporter gene in molecular biology and a potential candidate for suicide gene therapy applications in cancer treatment [PubMed: 11511870]. Its ability to accept a wide range of substrates makes it a versatile tool for both therapeutic and diagnostic purposes. However, the potential for viral resistance through J2R mutations remains a challenge in clinical settings [PubMed: 16439528].

Other names

J2RThymidine kinase (Vaccinia virus)Vaccinia virus J2R proteinPoxvirus thymidine kinase

The enzyme catalyzes the phosphorylation of thymidine and various nucleoside analogs to their monophosphate forms [UniProt P03902]. These monophosphates are then further phosphorylated by host cell kinases to triphosphates, which compete with natural nucleotides for incorporation into viral DNA by DNA polymerase, leading to chain termination or the production of defective viral genomes [DrugBank].