Analysis of mutational effects at the HPRT locus in human G(0) phase lymphocytes irradiated in vitro with gamma rays.
The mutational effects of ionising radiation at the hypoxanthine-guanine phosphoribosyl transferase (HPRT) locus were studied in human peripheral blood G(0) phase lymphocytes irradiated in vitro with gamma rays. The presence of radiation induced mutants was assessed by selecting the HPRT mutants every week on the basis of 6-thioguanine resistance up to 1 month after irradiation. A dose-related increase of 14.25x10(-6) mutants/Gy was measured after an expression time of 7 days. After 2 weeks from culture starting the fraction of clonable cells in irradiated and control cell populations decreased, limiting the measurements of mutant frequency. The mutational spectrum of the HPRT gene was determined by PCR analyses in a total of 99 mutant clones derived from irradiated lymphocytes. The independent origin of mutant clones carrying the same mutation was assessed by analysing the TCR gamma gene rearrangements. The results showed a dose-related increase of deletion mutants up to 3Gy, whereas point mutation frequency increased only up to 2Gy. Two preferentially deleted regions were identified; one involving the HPRT exon 3, and another one the 3'-terminal and the 3'-flanking region of the gene. One complex mutation involving a non-contiguous deletion of exons 2-5 and 7/8 was observed among the mutants isolated after 3Gy irradiation.
Dipartimento di Biologia, Università degli Studi di Padova, via U. Bassi 58B, 35121, Padova, Italy.
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Mognato
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Ferraro
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Canova
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Sordi
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Russo
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Cherubini
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Celotti
D001483:Base Sequence; D002470:Cell Survival / Q000235:genetics / Q000528:radiation effects; D017931:DNA Primers; D005720:Gamma Rays; D017353:Gene Deletion; D015334:Gene Rearrangement, gamma-Chain T-Cell Antigen Receptor; D006801:Humans; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics*; D008214:Lymphocytes / Q000201:enzymology / Q000528:radiation effects*; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D016192:Resting Phase, Cell Cycle
D017931:DNA Primers; D007041:Hypoxanthine Phosphoribosyltransferase