Viral thymidine kinases and their relatives

Gentry, Glenn A.

doi:10.1016/0163-7258(92)90006-l

Cited by 68 publications

(64 citation statements)

References 167 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…TK1 is a cytosolic, cell cycle-dependent enzyme with highest levels of activity during S phase [21][22][23]. TK2 is independent of the cell cycle and localized in the mitochondria [24][25][26]. Thymidine analogs, FLT and FMAU, have high retention in tumor tissue and are used for PET tumor imaging [6,7].…”

Section: Discussionmentioning

confidence: 99%

Tracking cellular stress with labeled FMAU reflects changes in mitochondrial TK2

Tehrani

Douglas

Lawhorn-Crews

et al. 2008

Eur J Nucl Med Mol Imaging

View full text Add to dashboard Cite

Purpose-Fluoropyrimidines like 1-(2 -deoxy-2 -fluoro--D-arabinofuranosyl)-thymine (FMAU) and 3 -deoxy-3 -fluorothymidine (FLT) accumulate in tumors and are being used as positron emission tomography tumor-imaging tracers. Proliferating tissues with high thymidine kinase 1 (TK1) activity retain FLT; however, the mechanism of selective accumulation of FMAU in tumors and certain other tissues requires further study.Methods-Retention of [ 3 H]FLT and [ 3 H]FMAU was measured in prostate cancer cell lines PC3, LNCaP, DU145, and the breast cancer cell line MD-MBA-231, and the tracer metabolites were analyzed by high-performance liquid chromatography (HPLC). FMAU retention, thymidine kinase 2 (TK2) activity, and mitochondrial mass were determined in cells stressed by depleted cell culture medium or by treating with oxidative, reductive, and energy stress, or specific adenosine monophosphate-activated protein kinase activator, or eIF2 inhibitor. TK1 and TK2 activities and mitochondrial mass were determined by FLT phosphorylation, 1--D-arabinofuranosylthymine (Ara-T) phosphorylation, and flow cytometry, respectively.Results-FMAU retention in rapidly proliferating cancer cell lines was five to ten times lower than FLT after 10 min incubation. HPLC analysis of the cellular extracts showed that phosphorylated tracers are the main retained metabolites. Nutritional stress decreased TK1 activity and FLT retention but increased retained FMAU. TK2 inhibition decreased FMAU retention and phosphorylation with negligible effects on FLT. Oxidative, reductive, or energy stress increased FMAU retention and correlated with mitochondrial mass (r 2 = 0.88, p=0.006). FMAU phosphorylation correlated with increased TK2 activity (r 2 =0.87, p=0.0002).Conclusion-FMAU is preferably phosphorylated by TK2 and can track TK2 activity and mitochondrial mass in cellular stress. FMAU may provide an early marker of treatment effects.

show abstract

Section: Discussionmentioning

confidence: 99%

Tracking cellular stress with labeled FMAU reflects changes in mitochondrial TK2

Tehrani

Douglas

Lawhorn-Crews

et al. 2008

Eur J Nucl Med Mol Imaging

View full text Add to dashboard Cite

show abstract

“…Site 3, consisting of the motif -DRH-, comprises three hydrophilic residues. The arginine at position 393 (Arg 393 ) is highly conserved among all TKs (the single amino acid and its position in the EBV TK was designated as Arg 393 ), suggesting its importance in the evolution of herpesviral TKs [40]. This site is important for TK activity and has been suggested to be involved in nucleoside recognition [32,35].…”

Section: Alignment Of Five Human Herpesvirus Tksmentioning

confidence: 99%

Identification and characterization of the conserved nucleoside-binding sites in the Epstein-Barr virus thymidine kinase

Chen

Chang

et al. 2004

Biochemical Journal

View full text Add to dashboard Cite

Thymidine kinase (TK), encoded by EBV (Epstein-Barr virus), is an attractive target for antiviral therapy and provides a novel approach to the treatment of EBV-associated malignancies. Despite the extensive use of nucleoside analogues for the treatment of viral infections and cancer, the structure-function relationship of EBV TK has been addressed rarely. In the absence of any structural information, we sought to identify and elucidate the functional roles of amino acids in the nucleoside-binding site using site-directed mutagenesis. Through alignment with other human herpesviral TK protein sequences, we predicted that certain conserved regions comprise the nucleoside-binding site of EBV TK and, through site-directed mutagenesis, showed significant changes in activity and binding affinity for thymidine of site 3 (-DRH-) and 4 (-VFP-) mutants. For site 3, only mutants D392E (Asp 392 → Glu) and R393H retain activity, indicating that a negative charge is important for Asp 392 and a positive charge is required for Arg 393 . The increased binding affinities of these two mutants for 3 -deoxy-2 ,3 -didehydrothymidine suggest that the two residues are also important for substrate selection. Interestingly, the changed metal-ion usage pattern of D392E reveals that Asp 392 plays multiple roles in this region. His 394 cannot be compensated by other amino acids, also indicating a crucial role. In site 4, the F402Y mutant retains full activity; however, F402S retains only 60 % relative activity. Strikingly, when Phe 402 is substituted with serine residue, the original preferred pyrimidine substrates, such as 3 -azido-3 -deoxythymidine, iododeoxyuridine and β-L-5-iododioxolane uracil (L-form substrate), have decreased competitiveness with thymidine, suggesting that Phe 402 plays a crucial role in substrate specificity and that the aromatic ring is important for function.

show abstract

“…The enzyme has been intensively studied over the past few decades because of its roles in cell proliferation, apoptosis and antiviral drug activation [18]. TK is not only widely distributed in eukaryotes and prokaryotes, but also present in a number of large DNA viruses, such as herpesviruses, poxviruses, asfaviruses, and whispoviruses [19][20][21][22]. However, viral TKs also belong to different subfamilies based on the sequence homology and substrate specificity [19,20,23].…”

Section: Introductionmentioning

confidence: 99%

“…TK is not only widely distributed in eukaryotes and prokaryotes, but also present in a number of large DNA viruses, such as herpesviruses, poxviruses, asfaviruses, and whispoviruses [19][20][21][22]. However, viral TKs also belong to different subfamilies based on the sequence homology and substrate specificity [19,20,23]. For example, herpesvirus TKs have relatively broad substrate specificity such that they can phosphorylate deoxycytidine (dC) [24] and thymidine monophosphate (TMP) [25].…”

Section: Introductionmentioning

confidence: 99%

Rana grylio virus thymidine kinase gene: an early gene of iridovirus encoding for a cytoplasmic protein

et al. 2009

View full text Add to dashboard Cite

The presence of thymidine kinase (TK) is a feature of many large DNA viruses. Here, a TK gene homologue was cloned and characterized from Rana grylio virus (RGV), a member of family Iridoviridae. RGV TK encodes a protein of 195 aa with a predicted molecular mass of 22.1 kDa. Homologues of the protein were present in all the currently sequenced iridoviruses, and phylogenetic analysis showed that it was much close to cellular TK type 2 (TK2), deoxycytidine kinase (dCK) and deoxyguanosine kinase (dGK). Subsequently, Western blotting revealed TK expression increased with time from 6 h postinfection in RGV-infected cells. Using drug inhibition analysis by protein synthesis inhibitor (cycloheximide) and DNA replication inhibitor (cytosine arabinofuranoside), RGV TK was classified as the early expression gene during in vitro infection. Subcellular localization by TK-GFP fusion protein expression and immunofluorescence staining showed RGV TK was an exclusively cytoplasmic protein in fish cells. Collectively, current data indicate that RGV TK was an early gene of iridovirus which encoded a cytoplasmic protein in fish cells.

show abstract

Viral thymidine kinases and their relatives

Cited by 68 publications

References 167 publications

Tracking cellular stress with labeled FMAU reflects changes in mitochondrial TK2

Tracking cellular stress with labeled FMAU reflects changes in mitochondrial TK2

Identification and characterization of the conserved nucleoside-binding sites in the Epstein-Barr virus thymidine kinase

Rana grylio virus thymidine kinase gene: an early gene of iridovirus encoding for a cytoplasmic protein

Contact Info

Product

Resources

About