1
|
Wright GM, Menzel J, Tatman PD, Black JC. Transition from Transient DNA Rereplication to Inherited Gene Amplification Following Prolonged Environmental Stress. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.08.539886. [PMID: 37214911 PMCID: PMC10197558 DOI: 10.1101/2023.05.08.539886] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Cells require the ability to adapt to changing environmental conditions, however, it is unclear how these changes elicit stable permanent changes in genomes. We demonstrate that, in response to environmental metal exposure, the metallothionein (MT) locus undergoes DNA rereplication generating transient site-specific gene amplifications (TSSGs). Chronic metal exposure allows transition from MT TSSG to inherited MT gene amplification through homologous recombination within and outside of the MT locus. DNA rereplication of the MT locus is suppressed by H3K27me3 and EZH2. Long-term ablation of EZH2 activity eventually leads to integration and inheritance of MT gene amplifications without the selective pressure of metal exposure. The rereplication and inheritance of MT gene amplification is an evolutionarily conserved response to environmental metal from yeast to human. Our results describe a new paradigm for adaptation to environmental stress where targeted, transient DNA rereplication precedes stable inherited gene amplification.
Collapse
|
2
|
Perepnikhatka V, Fischer FJ, Niimi M, Baker RA, Cannon RD, Wang YK, Sherman F, Rustchenko E. Specific chromosome alterations in fluconazole-resistant mutants of Candida albicans. J Bacteriol 1999; 181:4041-9. [PMID: 10383973 PMCID: PMC93895 DOI: 10.1128/jb.181.13.4041-4049.1999] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/1999] [Accepted: 04/23/1999] [Indexed: 11/20/2022] Open
Abstract
The exposure of Candida albicans to fluconazole resulted in the nondisjunction of two specific chromosomes in 17 drug-resistant mutants, each obtained by an independent mutational event. The chromosomal changes occurred at high frequencies and were related to the duration of the drug exposure. The loss of one homologue of chromosome 4 occurred after incubation on a fluconazole medium for 7 days. A second change, the gain of one copy of chromosome 3, was observed after exposure for 35 or 40 days. We found that the mRNA levels of ERG11, CDR1, CDR2, and MDR1, the candidate fluconazole resistance genes, remained either the same or were diminished. The lack of overexpression of putative drug pumps or the drug target indicated that some other mechanism(s) may be operating. The fluconazole resistance phenotype, electrophoretic karyotypes, and transcript levels of mutants were stable after growth for 112 generations in the absence of fluconazole. This is the first report to demonstrate that resistance to fluconazole can be dependent on chromosomal nondisjunction. Furthermore, we suggest that a low-level resistance to fluconazole arising during the early stages of clinical treatment may occur by this mechanism. These results support our earlier hypothesis that changes in C. albicans chromosome number is a common means to control a resource of potentially beneficial genes that are related to important cellular functions.
Collapse
Affiliation(s)
- V Perepnikhatka
- Department of Biochemistry and Biophysics, University of Rochester Medical School, Rochester, New York 14642, USA
| | | | | | | | | | | | | | | |
Collapse
|
3
|
Abstract
The process of programmed cell death, or apoptosis, has become one of the most intensively studied topics in biological sciences in the last two decades. Apoptosis as a common and universal mechanism of cell death, distinguishable from necrosis, is now a widely accepted concept after the landmark paper by Kerr, Wyllie and Currie in the early seventies [1]. Different components of the death machinery in eukaryotes are discussed in this issue.
Collapse
Affiliation(s)
- A Samali
- Department of Biochemistry, University College, Lee Maltings, Cork, Ireland
| | | | | |
Collapse
|
4
|
Turner JS, Robinson NJ. Cyanobacterial metallothioneins: biochemistry and molecular genetics. JOURNAL OF INDUSTRIAL MICROBIOLOGY 1995; 14:119-25. [PMID: 7766203 DOI: 10.1007/bf01569893] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Metallothioneins have been extensively studied in many different eukaryotes where they sequester, and hence detoxify, excess amounts of certain metal ions. However, the precise functions of many of these molecules are not fully understood. This article reviews literature concerning their namesakes in prokaryotes.
Collapse
Affiliation(s)
- J S Turner
- Department of Biochemistry and Genetics, Medical School, University of Newcastle, UK
| | | |
Collapse
|
5
|
Affiliation(s)
- N J Robinson
- Department of Biological Sciences, University of Durham, U.K
| | | | | | | |
Collapse
|
6
|
Coordinate induction of metallothioneins I and II in rodent cells by UV irradiation. Mol Cell Biol 1989. [PMID: 2463464 DOI: 10.1128/mcb.8.11.4716] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sequence analysis of Chinese hamster V79 lung fibroblast cDNA clones, which code for UV radiation-inducible transcripts, revealed that many of the clones corresponded to metallothioneins (MTs) I and II. A third cDNA clone, DDIU4, was found also to code for a similar-size UV-inducible transcript which was unrelated to MT by both sequence analysis and kinetics of induction. MTI and MTII RNAs rapidly increased in V79 cells within 1 h after UV irradiation, and maximum induction was seen by 4 h. This rapid induction of MT RNA by UV irradiation was not observed in human fibroblasts. MTI and MTII were coordinately induced in both time course and dose-response experiments, although the induction of MTII, up to 30-fold, was three to four times greater than that of MTI. The induction of MT did not appear to be a general stress response, since no increase occurred after exposure to X rays or H2O2.
Collapse
|
7
|
Lauverjat S, Ballan-Dufrancais C, Wegnez M. Detoxification of cadmium. Ultrastructural study and electron-probe microanalysis of the midgut in a cadmium-resistant strain of Drosophila melanogaster. BIOLOGY OF METALS 1989; 2:97-107. [PMID: 2518373 DOI: 10.1007/bf01129208] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The midgut of a cadmium-resistant strain of Drosophila melanogaster has been studied at the ultrastructural level and by electron-probe microanalysis (EPMA). Chronic exposure to cadmium leads to a concentration of the metal in a lysosomal system developed in both anterior and posterior segments of the midgut, where it coexists with copper and sulfur. This mechanism apparently ensures a permanent cadmium detoxification and prevents cellular injury. Wild-type flies fed on a cadmium-contaminated medium manifest the same detoxification process. As a result of contamination, copper is stored along the entire length of the midgut, including a part of the middle-midgut previously named 'copper-accumulating region'. Our data demonstrate that the midgut, particularly the posterior segment, is an accumulative organ for both cadmium and copper. The involvement of the metallothionein system in the detoxification process is discussed.
Collapse
Affiliation(s)
- S Lauverjat
- Laboratoire d'Histophysiologie Fondamentale et Appliquée, Université, Paris, France
| | | | | |
Collapse
|
8
|
Fornace AJ, Alamo I, Hollander MC. DNA damage-inducible transcripts in mammalian cells. Proc Natl Acad Sci U S A 1988; 85:8800-4. [PMID: 3194391 PMCID: PMC282594 DOI: 10.1073/pnas.85.23.8800] [Citation(s) in RCA: 464] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Hybridization subtraction at low ratios of RNA to cDNA was used to enrich for the cDNA of transcripts increased in Chinese hamster cells after UV irradiation. Forty-nine different cDNA clones were isolated. Most coded for nonabundant transcripts rapidly induced 2- to 10-fold after UV irradiation. Only 2 of the 20 cDNA clones sequenced matched known sequences (metallothionein I and II). The predicted amino acid sequence of one cDNA had two localized areas of homology with the rat helix-destabilizing protein. These areas of homology were at the two DNA-binding sites of this nucleic acid single-strand-binding protein. The induced transcripts were separated into two general classes. Class I transcripts were induced by UV radiation and not by the alkylating agent methyl methanesulfonate. Class II transcripts were induced by UV radiation and by methyl methanesulfonate. Many class II transcripts were induced also by H2O2 and various alkylating agents but not by heat shock, phorbol 12-tetradecanoate 13-acetate, or DNA-damaging agents which do not produce high levels of base damage. Since many of the cDNA clones coded for transcripts which were induced rapidly and only by certain types of DNA-damaging agents, their induction is likely a specific response to such damage rather than a general response to cell injury.
Collapse
Affiliation(s)
- A J Fornace
- Radiation Oncology Branch, National Cancer Institute, Bethesda, MD 20892
| | | | | |
Collapse
|
9
|
Fornace AJ, Schalch H, Alamo I. Coordinate induction of metallothioneins I and II in rodent cells by UV irradiation. Mol Cell Biol 1988; 8:4716-20. [PMID: 2463464 PMCID: PMC365562 DOI: 10.1128/mcb.8.11.4716-4720.1988] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Sequence analysis of Chinese hamster V79 lung fibroblast cDNA clones, which code for UV radiation-inducible transcripts, revealed that many of the clones corresponded to metallothioneins (MTs) I and II. A third cDNA clone, DDIU4, was found also to code for a similar-size UV-inducible transcript which was unrelated to MT by both sequence analysis and kinetics of induction. MTI and MTII RNAs rapidly increased in V79 cells within 1 h after UV irradiation, and maximum induction was seen by 4 h. This rapid induction of MT RNA by UV irradiation was not observed in human fibroblasts. MTI and MTII were coordinately induced in both time course and dose-response experiments, although the induction of MTII, up to 30-fold, was three to four times greater than that of MTI. The induction of MT did not appear to be a general stress response, since no increase occurred after exposure to X rays or H2O2.
Collapse
Affiliation(s)
- A J Fornace
- Radiation Oncology Branch, National Cancer Institute, Bethesda, Maryland 20892
| | | | | |
Collapse
|
10
|
Okumoto DS, Bohr VA. DNA repair in the metallothionein gene increases with transcriptional activation. Nucleic Acids Res 1987; 15:10021-30. [PMID: 2827103 PMCID: PMC306548 DOI: 10.1093/nar/15.23.10021] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
We have studied DNA repair in the Chinese Hamster Ovary (CHO) metallothionein (MT) gene after UV-light induced damage. The repair was examined comparatively with or without transcriptional activation of the gene by incubation in the presence of the heavy metal ZnCl2. Whereas the repair efficiency was very low in the uninduced state, it increased significantly after induction of the gene. The presence of ZnCl2 did not appear to change other repair parameters in the cells. The overall genome DNA repair efficiency after UV irradiation was similar whether or not the gene was induced and the preferential DNA repair pattern in the essential dihydrofolate reductase (DHFR) gene which we have previously described was unaffected by the presence of ZnCl2. Based upon repair analysis in two different restriction fragments containing the MT I gene, we conclude that the region of efficient repair after induction is considerably larger than the 1 kb size of the gene. The results suggest that the accessibility of a genomic region to DNA repair enzymes may be regulated by the local chromatin structure in a dynamic manner.
Collapse
Affiliation(s)
- D S Okumoto
- Laboratory of Molecular Pharmacology, National Cancer Institute, Bethesda, MD 20892
| | | |
Collapse
|
11
|
|
12
|
Azacytidine-induced reactivation of a DNA repair gene in Chinese hamster ovary cells. Mol Cell Biol 1987. [PMID: 2431295 DOI: 10.1128/mcb.6.8.2944] [Citation(s) in RCA: 67] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Six X-ray-sensitive (xrs) strains of the CHO-K1 cell line were shown to revert at a very high frequency after treatment with 5-azacytidine. This suggested that there was a methylated xrs+ gene in these strains which was structurally intact, but not expressed. The xrs strains did not complement one another, and the locus was autosomally located. In view of the frequency of their isolation and their somewhat different phenotypes, we propose that the xrs strains are mutants derived from an active wild-type gene. However, there is in addition a methylated silent gene present in the genome. Azacytidine treatment reactivated this gene. We present a model for the functional hemizygosity of mammalian cell lines, which is based on the inactivation of genes by de novo hypermethylation. In contrast to results with xrs strains, other repair-defective lines were found not to be reverted by azacytidine.
Collapse
|
13
|
Coordinate expression of amplified metallothionein I and II genes in cadmium-resistant Chinese hamster cells. Mol Cell Biol 1986. [PMID: 3837847 DOI: 10.1128/mcb.5.12.3525] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Recombinant DNA probes complementary to Chinese hamster metallothionein (MT)-1 and MT-2 mRNAs were used to compare MT gene copy numbers, zinc-induced MT mRNA levels, and uninduced MT mRNA levels in cadmium-resistant (Cdr) Chinese hamster ovary cell lines. Quantitative hybridization analyses determined that the MT-1 and MT-2 genes are each present at approximately single-copy levels in the genome of cell line Cdr2C10 and are coordinately amplified approximately 7, 3, and 12 times over the Cdr2C10 value in the genomes of cell lines Cdr20F4, Cdr30F9, and Cdr200T1, respectively. The maximum zinc-induced MT-1 mRNA concentrations in cell lines Cdr20F4, Cdr30F9, and Cdr200T1 were equal to 1, 3, and 15 times that measured in Cdr2C10, respectively. Similarly, the maximum zinc-induced MT-2 mRNA concentrations were equal to 1, 3, and 14 times that measured in Cdr2C10, respectively, and in each instance they were 90 to 150 times greater than their respective concentrations in uninduced cells. Thus, relative MT gene numbers are closely correlated with both zinc-induced and uninduced MT mRNA levels in Cdr2C10, Cdr30F9, and Cdr200T1, but not in Cdr20F4. Each of the latter two lines possesses structurally altered chromosomes whose breakpoints are near the MT locus. Nonetheless, the ratio of the levels of MT-1 to MT-2 mRNAs was constant in each of the four cell lines, including Cdr20F4. These results demonstrate that MT-1 and MT-2 mRNAs are induced coordinately in each Cdr cell line. Therefore, the coordination of the induction of MT-1 and MT-2 mRNA is independent of MT gene amplification, MT gene rearrangement, and the relative inducibilities of amplified MT genes. However, MT mRNA and protein levels each indicate that MT-1 and MT-2 expression is non-coordinate in uninduced cells. Thus, regulation of MT expression may involve two different mechanisms which are differentially operative in induced and uninduced cells.
Collapse
|
14
|
Jeggo PA, Holliday R. Azacytidine-induced reactivation of a DNA repair gene in Chinese hamster ovary cells. Mol Cell Biol 1986; 6:2944-9. [PMID: 2431295 PMCID: PMC367863 DOI: 10.1128/mcb.6.8.2944-2949.1986] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Six X-ray-sensitive (xrs) strains of the CHO-K1 cell line were shown to revert at a very high frequency after treatment with 5-azacytidine. This suggested that there was a methylated xrs+ gene in these strains which was structurally intact, but not expressed. The xrs strains did not complement one another, and the locus was autosomally located. In view of the frequency of their isolation and their somewhat different phenotypes, we propose that the xrs strains are mutants derived from an active wild-type gene. However, there is in addition a methylated silent gene present in the genome. Azacytidine treatment reactivated this gene. We present a model for the functional hemizygosity of mammalian cell lines, which is based on the inactivation of genes by de novo hypermethylation. In contrast to results with xrs strains, other repair-defective lines were found not to be reverted by azacytidine.
Collapse
|
15
|
Vormann J, Höllriegl V, Merker HJ, Günther T. Effect of valproate on zinc metabolism in fetal and maternal rats fed normal and zinc-deficient diets. Biol Trace Elem Res 1986; 10:25-35. [PMID: 24254325 DOI: 10.1007/bf02795316] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/1985] [Accepted: 12/31/1985] [Indexed: 11/29/2022]
Abstract
Pregnant Wistar rats fed control and Zn-deficient diets received daily oral doses of 0, 100, and 300 mg/kg sodium valproate from d 16 to 20 of gestation. Only the highest valproate doses induced a small reduction in fetal body weight in the normally fed group. Zinc deficiency caused a drastic reduction in maternal and only a small reduction in fetal serum Zn concentrations. Valproate treatment had no effect on maternal and fetal serum Zn concentrations.Valproate reduced fetal liver Zn content only in the normally fed group. The reduction of liver Zn content resulted from the reduction of Zn-metallothionein. Valproate did not affect total Zn and Zn-metallothionein in kidneys. Three percent of the Zn-deficient fetuses developed hydronephrosis and hydrops. Valproate treatment drastically enhanced the occurrence of fetal hydronephrosis and hydrops. Valproate induced fetal liver necroses, independent of Zn nutrition.
Collapse
Affiliation(s)
- J Vormann
- Institute of Molecular Biology and Biochemistry, Free University of Berlin, Arnimallee 22, D-1000, Berlin 33, FRG
| | | | | | | |
Collapse
|
16
|
Griffith JK. Coordinate expression of amplified metallothionein I and II genes in cadmium-resistant Chinese hamster cells. Mol Cell Biol 1985; 5:3525-31. [PMID: 3837847 PMCID: PMC369183 DOI: 10.1128/mcb.5.12.3525-3531.1985] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Recombinant DNA probes complementary to Chinese hamster metallothionein (MT)-1 and MT-2 mRNAs were used to compare MT gene copy numbers, zinc-induced MT mRNA levels, and uninduced MT mRNA levels in cadmium-resistant (Cdr) Chinese hamster ovary cell lines. Quantitative hybridization analyses determined that the MT-1 and MT-2 genes are each present at approximately single-copy levels in the genome of cell line Cdr2C10 and are coordinately amplified approximately 7, 3, and 12 times over the Cdr2C10 value in the genomes of cell lines Cdr20F4, Cdr30F9, and Cdr200T1, respectively. The maximum zinc-induced MT-1 mRNA concentrations in cell lines Cdr20F4, Cdr30F9, and Cdr200T1 were equal to 1, 3, and 15 times that measured in Cdr2C10, respectively. Similarly, the maximum zinc-induced MT-2 mRNA concentrations were equal to 1, 3, and 14 times that measured in Cdr2C10, respectively, and in each instance they were 90 to 150 times greater than their respective concentrations in uninduced cells. Thus, relative MT gene numbers are closely correlated with both zinc-induced and uninduced MT mRNA levels in Cdr2C10, Cdr30F9, and Cdr200T1, but not in Cdr20F4. Each of the latter two lines possesses structurally altered chromosomes whose breakpoints are near the MT locus. Nonetheless, the ratio of the levels of MT-1 to MT-2 mRNAs was constant in each of the four cell lines, including Cdr20F4. These results demonstrate that MT-1 and MT-2 mRNAs are induced coordinately in each Cdr cell line. Therefore, the coordination of the induction of MT-1 and MT-2 mRNA is independent of MT gene amplification, MT gene rearrangement, and the relative inducibilities of amplified MT genes. However, MT mRNA and protein levels each indicate that MT-1 and MT-2 expression is non-coordinate in uninduced cells. Thus, regulation of MT expression may involve two different mechanisms which are differentially operative in induced and uninduced cells.
Collapse
|
17
|
Stallings RL, Munk AC, Longmire JL, Jett JH, Wilder ME, Siciliano MJ, Adair GM, Crawford BD. Oncogenes and linkage groups: conservation during mammalian chromosome evolution. Chromosoma 1985; 92:156-63. [PMID: 4006599 DOI: 10.1007/bf00328468] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Proto-oncogenes, which represent the cellular progenitors of the transforming genes harbored by acute transforming oncogenic retroviruses, have been highly conserved during vertebrate evolution. In this report, we have assigned experimentally a subset of proto-oncogenes (SRC, ABL, FES, and FMS-all related to the SRC family) to Chinese hamster chromosomes by Southern filter hybridization analyses of DNAs isolated from both somatic cell hybrids and flow-sorted hamster chromosomes. These results demonstrate that several autosomal linkage groups containing proto-oncogenes originated prior to the radiation and speciation of mammals and have remained remarkably stable for nearly 80 million years.
Collapse
|