Hprt: Gene Structure, Expression, and Mutation

Stout, J. Timothy; Caskey, C. Thomas

doi:10.1146/annurev.ge.19.120185.001015

Cited by 204 publications

(82 citation statements)

References 97 publications

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“…The hprt locus is widely used for the detection of mutagenic events (intra-locus and multilocus) in mammalian cells, including man (Vreling et al, 1985;Fuscoe et al, 1986;K6berle and Speit, 1991;Nicklas et al, 1991;Cole and Skopek, 1994). Most rodent studies have been carried out using Chinese hamster cells (Stout and Caskey, 1985;Nassi-Cal6 et al, 1989;K6berle and Speit, 1991;Schwartz et al, 1991) with relatively few studies in mouse cells (Evans et al, 1986;Vreling et al, 1988;Morita et al, 1991). A reported limitation to the use of the hprt locus (which is X linked and essentially single copy) for studies of clastogenic events is that concomitant loss of neighbouring essential genes (multilocus lesions) will result in non-viable mutants, i.e.…”

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Hprt mutants in a transplantable murine tumour arise more frequently in vivo than in vitro

Wilkinson

Sandhu²,

Breneman³

et al. 1995

Br J Cancer

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Sumnuary A model system was developed to allow investigation of the frequency at which clastogenic and or mutagenic events occur in situ in a transplantable murine fibrosarcoma tumour (MCIA-Cl) compared with in vitro culture. The marker selected for detecting these events was the X-linked hprt (hypoxanthine-guanine phosphonrbosyltransferase) gene. We found that the hprt gene in MCIA-Cl was not suitable for this purpose, most likely because multiple active copies were present. To circumvent the problem, HPRT -[6-thioguanine (6-TG)-resistant] clones were isolated by inactivating all hprt genes with methylnitrosourea. Spontaneous revertants to hypoxanthine/aminopterin/thymidine resistance (HATR) were isolated and found to be approximately 1000 times more sensitive than the parental tumour to induction of 6-TGR mutants by cobalt-60 y-rays. This sensitivity is expected for a heterozygous marker; these revertants may therefore possess only one functional hprt locus but two or more active X chromosomes. A clone with a stable hprt gene was identified and a neo gene was introduced. The resulting cell line (MN-i 1) could be grown as a subcutaneous tumour in syngeneic C57BL/6 animals. The frequency of mutations arising in vivo in the marker hprt gene could be estimated by cultunrng explanted tumour cells in the presence of 6-TG, using G418 selection to distinguish tumour from host cells. The frequency of mutants in MN-lI cells grown as tumours was found to be 3.4-fold higher than in tissue culture for an equivalent period of time. These data provide the first direct evidence for the existence of mutagenic factors in a tumour environment that might contribute to tumour progression.

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confidence: 99%

Hprt mutants in a transplantable murine tumour arise more frequently in vivo than in vitro

Wilkinson

Sandhu²,

Breneman³

et al. 1995

Br J Cancer

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“…Phosphoribosyltransferases also have attracted considerable attention because deficiency in these enzymes leads to various metabolic disorders in humans, e.g., Lesch-Nyhan disease (Stout & Caskey, 1985).…”

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Unexpected sequence similarity between nucleosidases and phosphoribosyltransferases of different specificity

Mushegian

Koonin

1994

Protein Science

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Amino acid sequences of enzymes that catalyze hydrolysis or phosphorolysis of the N-glycosidic bond in nucleosides and nucleotides (nucleosidases and phosphoribosyltransferases) were explored using computer methods for database similarity search and multiple alignment. Two new families, each including bacterial and eukaryotic enzymes, were identified. Family I consists of Escherichia coli AMP hydrolase (Amn), uridine phosphorylase (Udp), purine phosphorylase (DeoD), uncharacterized proteins from E. coli and Bacteroides uniformis, and, unexpectedly, a group of plant stress-inducible proteins. It is hypothesized that these plant proteins have evolved from nucleosidases and may possess nucleosidase activity. The proteins in this new family contain 3 conserved motifs, one of which was found also in eukaryotic purine nucleosidases, where it corresponds to the nucleoside-binding site. Family I1 is comprised of bacterial and eukaryotic thymidine phosphorylases and anthranilate phosphoribosyltransferases, the relationship between which has not been suspected previously. Based on the known tertiary structure of E. coli thymidine phosphorylase, structural interpretation was given to the sequence conservation in this family. The highest conservation is observed in the N-terminal a-helical domain, whose exact function is not known.Parts of the conserved active site of thymidine phosphorylases and anthranilate phosphoribosyltransferases were delineated. A motif in the putative phosphate-binding site is conserved in family I1 and in other phosphoribosyltransferases. Our analysis suggests that certain enzymes of very similar specificity, e.g., uridine and thymidine phosphorylases, could have evolved independently. In contrast, enzymes catalyzing such different reactions as AMP hydrolysis and uridine phosphorolysis or thymidine phosphorolysis and phosphoribosyl anthranilate synthesis are likely to have evolved from common ancestors.

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“…HPRT is a single copy gene located on the X-chromosome, and thus one copy is present in male cells. The mono-allelic nature of HPRT expression is convenient for measuring mutation frequencies and types [23]. We hypothesized that X-ray-induced DNA dsbs were repaired with greater accuracy in CRR cells compared with parental cells.…”

Section: Introductionmentioning

confidence: 99%

X-Ray Induced Mutation Frequency at the <i>Hypoxanthine Phosphoribosyltransferase</i> Locus in Clinically Relevant Radioresistant Cells

Kuwahara¹,

Roudkenar²,

Urushihara³

et al. 2017

IJMPCERO

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To elucidate the molecular mechanisms underlying cellular radioresistance, clinically relevant radioresistant cell lines were established via long-term exposure to X-rays with stepwise dose escalation. Established cells continue to proliferate despite exposure to 2 Gy X-rays/day for more than 30 days, a standard protocol in cancer radiotherapy. DNA repair fidelity in radioresistant and the parental cells by evaluating the mutation frequency at the hypoxanthine phosphoribosyltransferase (HPRT) locus after exposure to X-rays was determined. Mutation spectrum at the HPRT locus was examined by multiplex polymerase chain reaction. Rejoining kinetics of X-ray-induced DNA double strand breaks (dsbs) was evaluated by the detection of phosphorylated histone H2AX (γH2AX) after X-irradiation. The fold increase in the HPRT mutation frequency due to acute radiation was similar between radioresistant and the parental cell lines. However, fractionated radiation (FR) consisting of 2 Gy X-rays/day increased the mutation frequency at the HPRT locus in parental but not in radioresistant cells. Analysis of the FR-induced mutations at the HPRT locus revealed a high frequency of deletion mutations (>70%) in parental but not in

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Hprt: Gene Structure, Expression, and Mutation

Cited by 204 publications

References 97 publications

Hprt mutants in a transplantable murine tumour arise more frequently in vivo than in vitro

Hprt mutants in a transplantable murine tumour arise more frequently in vivo than in vitro

Unexpected sequence similarity between nucleosidases and phosphoribosyltransferases of different specificity

X-Ray Induced Mutation Frequency at the <i>Hypoxanthine Phosphoribosyltransferase</i> Locus in Clinically Relevant Radioresistant Cells

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Hprt: Gene Structure, Expression, and Mutation

Cited by 204 publications

References 97 publications

Hprt mutants in a transplantable murine tumour arise more frequently in vivo than in vitro

Hprt mutants in a transplantable murine tumour arise more frequently in vivo than in vitro

Unexpected sequence similarity between nucleosidases and phosphoribosyltransferases of different specificity

X-Ray Induced Mutation Frequency at the &lt;i&gt;Hypoxanthine Phosphoribosyltransferase&lt;/i&gt; Locus in Clinically Relevant Radioresistant Cells

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X-Ray Induced Mutation Frequency at the <i>Hypoxanthine Phosphoribosyltransferase</i> Locus in Clinically Relevant Radioresistant Cells