How thymidine kinase gene act as a selection marker?
The human herpes simplex virus thymidine kinase type 1 gene (HSVtk) acts as a conditional lethal marker in mammalian cells. The HSVtk-encoded enzyme is able to phosphorylate certain nucleoside analogs (e.g. ganciclovir, an antiherpetic drug), thus converting them to toxic DNA replication inhibitors.
What is the function of viral thymidine kinase?
Thymidine kinase or deoxyribonucleoside kinase (TK) catalyzes the conversion of deoxythymidine (THM) to deoxythymidine 5′-phosphate (THMP) with the conversion of ATP to ADP. TK has an important role in the synthesis of DNA. It is required for the action of many antiviral drugs. Higher organisms have 2 isozymes.
How does thymidine kinase work?
Thymidine kinase (TK) activity is measured by radioenzymatic assay. TK is an enzyme that catalyses the phosphorylation of deoxythymidine to deoxythymidine monophosphate. Its activity is highest in G1-S translation checkpoint and then declines rapidly in the G2 phase of the cell cycle.
What is the mechanism of acyclovir?
Mechanism of Action: Acyclovir is converted to its triphosphate form, acyclovir triphosphate (ACV-TP), which competitively inhibits viral DNA polymerase, incorporates into and terminates the growing viral DNA chain, and inactivates the viral DNA polymerase.
Does CMV have thymidine kinase?
The major difference is that CMV does not contain a thymidine kinase. Protein UL97 phosphorylates ganciclovir to ganciclovir monophosphate. One of the mechanisms of ganciclovir resistance is a change in UL97.
What type of molecular target is TK1?
Thymidine kinase 1 (TK1) is a DNA salvage pathway enzyme involved in regenerating thymidine for DNA synthesis and DNA damage.
Why is ganciclovir toxic to cells that are expressing the viral thymidine kinase enzyme?
This high toxicity may be attributable to the avid incorporation and lengthy retention of GCV into DNA. GCV triphosphate and its incorporation into the nascent DNA strand do not produce strong inhibition of DNA synthesis, so cells incorporate high levels of this drug, complete DNA replication and go on to divide.
What does acyclovir do to the virus?
Acyclovir is in a class of antiviral medications called synthetic nucleoside analogues. It works by stopping the spread of the herpes virus in the body.
Why is acyclovir selectively toxic to viral replication?
Further selective toxicity is derived from the fact that acyclovir triphosphate is selectively taken up by viral α-DNA polymerases because its structure resembles that of the essential DNA precursor, 2′-deoxyguanosine triphosphate.
Is Valganciclovir an antiviral?
Valganciclovir is an antiviral. It is used to treat infections caused by viruses. This medicine is also used to prevent CMV disease in patients who have received an organ transplant (eg, heart, kidney, or kidney-pancreas transplant).
What does TK1 stand for?
Thymidine kinase 1 (TK1) is a key enzyme in DNA precursor synthesis. It is upregulated during the S phase of the cell cycle and its presence in cells is an indicator of active cell proliferation.