Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.1.21 (thymidine kinase)
7,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The kinetics of formation, the stability at 40 degrees C and the serological properties of thymidine kinase and deoxycytidine kinase activities induced by herpes simplex virus have been examined. The results are consistent with the hypothesis that both activities are carried on the same molecule-a deoxypyrimidine kinase. Mutants deficient in deoxypyrimidine kinase have been used to produce, by absorption of general antisera, deoxypyrimidine kinase-specific antisera. Using immunoprecipitation and SDS-polyacrylamide gel electrophoresis, only one size of polypeptide (mol. wt. 42400 plus or minus 200) has been found, constituting the type 2 enzyme. This is close to published values for the type i enzyme but co-electrophoresis demonstrated that the polypeptide of the type i enzyme was slightly bigger.
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PMID:Deoxypyrimidine kinases of herpes simplex viruses types 1 and 2: comparison of serological and structural properties. 16 87

To investigate the size of herpes simplex virus (HSV) thymidine kinase (TK) polypeptides, procedures have been devised to purify the enzyme from infected cells labeled with 35S-methionine by (i) affinity chromatography on Sepharose-5'-amino-5'-deoxythymidine; (ii) preparative isoelectric focusing or preparative PAGE; and (iii) glycerol gradient centrifugation. Portions of enzyme fractions, at each purification step, were also treated with an immunoadsorbent, Sepharose-anti-HSV-1 TK immunoglobulin (IgG). Labeled polypeptides eluted from the immunoadsorbent were analyzed by electrophoresis in SDS slab gels and autoradiography. The results demonstrate that the molecular weights of HSV TK polypeptides are about 40,000. TK-negative HSV-1 mutant B2006 failed to induce the 40 K dalton polypeptide.
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PMID:Detection of herpes simplex virus thymidine kinase polypeptides in cells labeled with 35S-methionine. 20 86

The cytoplasmic mRNA which codes for the herpes simplex virus specific thymidine kinase (TK) is polyadenylated and is 14.5s in size. This corresponds to an RNA of 1400 nucleotides. The TK polypeptide is about 42,000 daltons, which requires 1100 nucleotide. We conclude that the cytoplasmic mRNA is monocistronic. The reticulocyte lysate cell-free translation system synthesizes enzymatically active HSV-TK which can be assayed with high specificity and sensitivity by use of 125I-iododeoxycytidine as a substrate.
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PMID:Characterization of the mRNA for herpes simplex virus thymidine kinase by cell-free synthesis of active enzyme. 20 7

Varicella-zoster virus (VZV) gene 63 encodes a protein (IE63) with a predicted molecular mass of 30.5 kDa which has amino acid similarities to the immediate-early (IE) protein 22 (ICP22) of herpes simplex virus type 1. ICP22 is a polypeptide synthesized in herpes simplex virus type 1-infected cells, and as is the case for its VZV counterpart, its regulatory functions are unknown. On the basis of the VZV DNA sequence, it has been shown that IE63 exhibits hydrophilic and acidic properties, suggesting that this protein could play a regulatory role during the infectious cycle. We report in this article cotransfection experiments which demonstrate that the VZV gene 63 protein strongly represses, in a dose-dependent manner, the expression of VZV gene 62. On the other hand, transient expression of the VZV gene 63 protein can promote activation of the thymidine kinase gene but cannot affect the expression of the genes encoding glycoproteins I and II. The results of transient expression experiments strongly suggest that the VZV gene 63 protein could play a pivotal role in the repression of IE gene expression as well as in the activation of early gene expression.
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PMID:Characterization of regulatory functions of the varicella-zoster virus gene 63-encoded protein. 131 89

This report describes a novel method for complementation studies of defective herpes simplex virus (HSV) genes. Viral test gene and nonviral reporter gene cassettes were rapidly integrated into the HSV genome in a site-specific and reversible manner by using the P1 phage-based Cre-lox recombination system. Shuttle plasmids contained a functional loxP recombination site, an expressible form of the bacterial lacZ gene, and a copy of the wild-type glycoprotein B (gB) gene or double mutant gB allele containing both a temperature-sensitive (ts) mutation and a syncytium (syn)-forming mutation. A recipient viral genome, K delta T::lox1, was constructed from the HSV type 1 (syn) gB-deficient mutant virus, K delta T, by marker transfer of the loxP recombination site into the viral thymidine kinase locus. Shuttle plasmids of up to 12.9 kb in length were recombined with high efficiency (11 to 20%) into the K delta T::lox1 genome in cell-free, Cre-mediated recombination reactions. Expression of a functional wild-type or double mutant gB polypeptide complemented the nonfunctional polypeptide expressed from the deleted, normal gB locus and allowed production of either wild-type or Syn- plaques on Vero cells. The latter recombinant virus was also ts for growth. The ability to express viral genes from plasmids which can be shuttled into and out of the HSV genome in cell-free recombination reactions makes this a powerful method for performing genetic studies of the biologic properties of viral gene products.
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PMID:A cell-free recombination system for site-specific integration of multigenic shuttle plasmids into the herpes simplex virus type 1 genome. 132 9

Mouse mammary tumor virus (MMTV) is a milk-transmitted retrovirus involved in the neoplastic transformation of mouse mammary gland cells. The expression of this virus is regulated by mammary cell type-specific factors, steroid hormones, and polypeptide growth factors. Sequences for mammary cell-specific expression are located in an enhancer element in the extreme 5' end of the long terminal repeat region of this virus. This enhancer, when cloned in front of the herpes simplex thymidine kinase promoter, endows the promoter with mammary cell-specific response. Using functional and DNA-protein-binding studies with constructs mutated in the MMTV long terminal repeat enhancer, we have identified two main regulatory elements necessary for the mammary cell-specific response. These elements consist of binding sites for a transcription factor in the family of CTF/NFI proteins and the transcription factor mammary cell-activating factor (MAF) that recognizes the sequence G Pu Pu G C/G A A G G/T. Combinations of CTF/NFI- and MAF-binding sites or multiple copies of either one of these binding sites but not solitary binding sites mediate mammary cell-specific expression. The functional activities of these two regulatory elements are enhanced by another factor that binds to the core sequence ACAAAG. Interdigitated binding sites for CTF/NFI, MAF, and/or the ACAAAG factor are also found in the 5' upstream regions of genes encoding whey milk proteins from different species. These findings suggest that mammary cell-specific regulation is achieved by a concerted action of factors binding to multiple regulatory sites.
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PMID:A mammary cell-specific enhancer in mouse mammary tumor virus DNA is composed of multiple regulatory elements including binding sites for CTF/NFI and a novel transcription factor, mammary cell-activating factor. 132 67

A number of HSV-2 isolates, sequentially recovered from ulcerative ano-genital lesions of an AIDS patient during a prolonged treatment with acyclovir (ACV), have been studied at the molecular level. All of them were highly resistant to ACV (ACV-r) and shown to be virtually deficient in thymidine kinase (TK) activity. The ACV-r phenotype was demonstrated to be due to the production of truncated TK polypeptide. Structural alteration of this gene, as shown in one isolate, was caused by a chain-terminating mutation that originated from a cytidine deletion at position 520 of the TK open reading frame. This mutation generated a TGA stop codon 27 nucleotides downstream. An additional isolate was also recovered following ACV discontinuation and after a cycle of treatment with foscarnet. This isolate had lost the ACV-r trait and was characterized by a wild type TK sequence and by the production of a functional enzyme. Data presented confirm that a prolonged treatment with acyclovir can easily select ACV-r HSV-2 isolates carrying a TK- phenotype caused by a frameshift mutation. Although recovered from lesions tributary of different myelomers, these isolates may belong to the same strain that has undergone multiple cycles of reactivation and has possibly mutated during its axonal route to the skin.
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PMID:A point mutation in the thymidine kinase gene is responsible for acyclovir-resistance in herpes simplex virus type 2 sequential isolates. 132 74

Thymidine kinases were described for cellular life long before it was shown that they could also be encoded by viruses, but the viral thymidine kinase genes were the first to be sequenced. These enzymes have been extraordinarily useful to the researcher, serving first to help label DNA, then to get thymidine analogs incorporated into DNA for therapeutic and other purposes and more recently to move genes from one genome to another. Knowledge of the nucleotide and amino acid sequences of these enzymes has allowed some deductions about their possible three-dimensional structure, as well as the location on the polypeptide of various functions; it has also allowed their classification into two main groups: the herpesviral thymidine/eukaryotic deoxycytidine kinases and the poxviral and cellular thymidine kinases; the relationships of the mitochondrial enzyme are still not clear.
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PMID:Viral thymidine kinases and their relatives. 133 63

The location and nucleotide sequence of the bovine herpesvirus type 4 (BHV-4) thymidine kinase (TK) gene was determined. The coding region of the TK gene is 1335 nucleotides long and corresponds to a polypeptide of 445 amino acids. Comparison of TK amino acid sequences of BHV-4 and 16 herpesvirus TKs reveals a greater homology to those of the gammaherpesviruses EBV and specially HVS, than to those of alphaherpesviruses. The open reading frames detected in the vicinity of TK gene were homologous to the corresponding ones in other herpesviruses.
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PMID:Location and characterization of the bovine herpesvirus type 4 thymidine kinase gene; comparison with thymidine kinase genes of other herpesviruses. 133 65

Studies with molecular and immunological techniques identified and mapped the transcript encoding glycoprotein D (gD) of equine herpesvirus 1 KyA, as well as two continuous gD antigenic determinants. Three mRNA species of 5.5, 3.8, and 1.7 kb overlap the gD open reading frame and are transcribed from the DNA strand encoding gD. Northern (RNA) blot hybridization with both DNA clones and riboprobes, as well as S1 nuclease analyses, showed the 3.8-kb mRNA to encode gD and to be synthesized as a late (beta-gamma) transcript. The 3.8-kb gD mRNA initiates within the US segment 91 and 34 nucleotides downstream of the CCAAT and TATA elements, respectively, and encodes a potential polypeptide of 392 amino acids. The termination site of this transcript maps within the terminal repeat at a site also used by the 5.5-kb mRNA and the IR6-encoded 1.2-kb mRNA, such that these three transcripts form a 3'-coterminal nested set. The extended size (2,250 nucleotides) of the 3' untranslated region of the gD transcript and its termination within the terminal repeat may result from the deletion of 3,859 bp, which eliminates two consensus polyadenylation signals downstream of the gD open reading frame of EHV-1 KyA. Use of antisera to synthetic peptides of 19 amino acids (residues 4 to 22) and 20 amino acids (residues 267 to 285) in Western immunoblot analyses revealed that gD is present in EHV-1 virions as a 55-kDa polypeptide. In addition, these antisera detected the 55-kDa protein as well as 58- and 47-kDa polypeptides in infected-cell extracts at late times of infection. Residues 4 to 22 make up a continuous neutralizing epitope of gD, since incubation of equine herpesvirus 1 with the anti-19-mer serum prior to infection results in reduced numbers of plaques and reduced levels of virus-encoded thymidine kinase. Complement is not required for neutralization mediated by the anti-19-mer serum.
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PMID:Equine herpesvirus 1 glycoprotein D: mapping of the transcript and a neutralization epitope. 138 65


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