Repair of pyrimidine dimers in nuclear and mitochondrial DNA of yeast irradiated with low doses of ultraviolet light

Prakash, Louise

doi:10.1016/s0022-2836(75)80010-6

Cited by 151 publications

(51 citation statements)

References 28 publications

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“…4). The rate of DNA synthesis in these cdc8 cells was greatly reduced compared with that in wild-type cells (10 (30,43,44) or bypassed during DNA repliared from cells cation by a postreplication repair mechanism(s) (31). Since in panel A.…”

Section: Resultsmentioning

confidence: 97%

Regulation of CDC9, the Saccharomyces cerevisiae gene that encodes DNA ligase.

Peterson¹,

Prakash²,

Prakash³

et al. 1985

Mol. Cell. Biol.

110

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We have cloned CDC9, the structural gene for Saccharomyces cerevisiae DNA ligase, and investigated its transcriptional regulation both as a function of cell cycle stage and after UV irradiation. The steady-state level of DNA ligase mRNA increases at least fourfold in late G1, after the completion of start but before S phase. This high level of CDC9 mRNA then decays with an apparent half-life of ca. 20 min and remains at a low basal level throughout the rest of the cell cycle. The accumulation of CDC9 mRNA in late Gl is dependent upon the completion of start but not the CDC7 and CDC8 functions. Exposure of cells to UV light elicits an eightfold increase in DNA ligase mRNA levels.The yeast Saccharomyces cerevisiae offers the opportunity to combine sophisticated genetic and biochemical analyses to the study of eucaryotic cell division. In attempting to elucidate the molecular events of the cell division cycle, researchers have asked whether yeast genes are expressed periodically during the cell cycle. Initial studies on the activities of various enzymes in cultures of synchronously dividing cells did show significant periodic fluctuations in activity (21). However, subsequent work which examined synthesis of over 200 major yeast proteins found no evidence for periodic synthesis; instead, the proteins analyzed showed exponential synthesis during the cell cycle (7). It was suggested that the previously observed activity modulations were the result not of changes in enzyme synthesis but rather of periodic changes in regulatory molecules affecting enzyme activity (8). The only exceptions noted were the histones; these proteins did show a cell cycle periodicity in synthesis, being synthesized maximally in early S phase (7). Expression of the yeast histone genes is now known to be cell cycle regulated by both transcriptional and posttranscriptional controls (10, 13). To our knowledge, the histone genes and the homothallism gene HO (24) are the only identified yeast genes known to be subject to mitotic cell cycle regulation at the level of synthesis of gene products. However, a recent examination of ca. 900 5. cerevisiae proteins revealed eight other proteins of unknown identity which appeared to be synthesized periodically in the cell cycle (19).Of the many yeast cdc (cell division cycle) mutants isolated, cdc9 is one of the few in which the biochemical defect has been identified. Johnston and Nasmyth demonstrated that cdc9 mutants are defective in DNA ligase activity (17). While this manuscript was in preparation, we became aware that CDC9 was recently cloned and shown to encode a DNA ligase by virtue of its ability to complement the Schizosaccharomyces pombe cdcl7 mutation, which lies in the DNA ligase structural gene of that organism (1,25). We report here the independent molecular cloning and transcriptional characterization of CDC9.* Corresponding author.DNA ligase functions in at least three processes in vivo: DNA replication, repair, and recombination. Since DNA replication is periodic and levels of DNA repair and...

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Section: Resultsmentioning

confidence: 97%

Regulation of CDC9, the Saccharomyces cerevisiae gene that encodes DNA ligase.

Peterson¹,

Prakash²,

Prakash³

et al. 1985

Mol. Cell. Biol.

110

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“…Similarly, UV-in- duced pyrimidine dimers are not excised from mtDNA in yeast (27,28). However, the considerable degradation ofmtDNA that occurs after UV-treatment is not observed in the case of 8-(OMe)Ps photoaddition.…”

Section: Discussionmentioning

confidence: 99%

The fate of 8-methoxypsoralen photoinduced crosslinks in nuclear and mitochondrial yeast DNA: comparison of wild-type and repair-deficient strains.

Magaña‐Schwencke¹,

Henriques²,

Chanet³

et al. 1982

Proc. Natl. Acad. Sci. U.S.A.

193

135

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In, Saccharomyce8 cerevisiae, after 8-methoxypsoralen 18-(OMe)Ps] photoaddition, more crosslinks are induced per unit dose in mitochondrial DNA than in nuclear DNA. In wildtype cells treated.in the exponential phase of growth, single-and double-strand breaks are produced during crosslink removal and then are rejoined upon postexposure incubation. The incision step is almost blocked in the rad3-2 mutant, which is also defective in excision-repair of UV-induced (254 nm) pyrimidine dimers. The cutting of crosslinks from nuclear DNA is depressed in wild-type stationary-phase cells. This is correlated with a higher sensitivity of such cells to 8-(OMe)Ps photoinduced, cell killing. The incision of crosslinks is dramatically reduced in mitochondrial DNA. The rejoining ofsingle-and double-strand breaks is not only dependent on the product of the RAD51 gene (as shown by others) but also of the PS02 gene. A correlation was found.between the ability to recombine and strand rejoining. Therefore, as in bacteria, both the excision and the recombinational repair systems are. involved in crosslink repair in yeast. However, double-strand breaks in yeast constitute repair intermediates which are not detected in Eacherichia coli. The LD37 (dose necessary to induce a mean of one lethal hit per cell) corresponds to about 120 crosslinks per genome in.exponential-phase cells of the wild type and to 1-2 crosslinks in the p8o2-1 mutant.The psoralen derivative, 8-methoxypsoralen [8-(OMe)Ps] intercalates in DNA; upon exposure to near UV radiation, it reacts with pyrimidine bases to form monoadducts and interstrand crosslinks (1, 2). These photomodifications of DNA lead to lethality and induction of mutation and recombination (1-3). In addition, the production in yeast of the mitochondrial "petite" mutation (rho-) has been reported (4-6). Removal ofcrosslinks has been described in Escherichia coli (7-10) and in mammalian cells in culture (11,12). In E. coli, the excision and the recombinational repair pathways are involved in the restitution of an intact genome from DNA containing psoralen photoproducts (7,9,10). In eukaryotes, limited information is available on the molecular steps in relation to the genetic control of repair of crosslinks in DNA. On the basis of sensitivity to cell killing in rad mutants compared to the wild type, it was demonstrated that in the yeast Saccharomyces cerevisiae, in addition to the excision (rad3 type), the error-prone (rad6 type), and the DNA double-strand-break (rad52) repair pathways (5, 13), some repair steps controlled by a class of genes designated pso (14) also are implicated in the repair of this last type of lesion.In this report, we determined the proportion of 8-(OMe)Ps photoinduced crosslinks as a function ofdose and followed their fate in nuclear and mtDNA in a normal strain. The influence of the growth phases, known to modify the lethal response (15), on crosslink removal was studied. An excision-deficient mutant (rad3) and one of the pso mutants (pso2) defective in the G2-phase repai...

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“…The steady-state concentration of oxygen radicals may be even higher in tumor mitochondria since they have diminished amounts of superoxide dismutase [53,54] There is a general consensus that mitochondria are less efficient in repairing DNA damage and replication errors than the nucleus [56][57][58][59]. For example, they lack excision repair and recombinational repair [60,61]. Mitochondria do, however, possess three uracil DNA glycosylases [62][63][64], two endonuclease activities specific for apurinic/ apyrimidinic sites [Tomkinson, A.E.…”

Section: Mitochondria and Oxygenmentioning

confidence: 99%

Do mitochondrial DNA fragments promote cancer and aging?

Richter

1988

FEBS Letters

211

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Reactive oxygen species are important in carcinogenesis, diseases, and aging, probably through oxidative damage of DNA. Our understanding of this relationship at the molecular level is very sketchy. It has recently been found that in mitochondria oxidative DNA damage is particularly high and may not be repaired efficiently. I propose that oxidatively generated DNA fragments escape from mitochondria and become integrated into the nuclear genome. This may transform cells to a cancerous state. Time‐dependent nuclear accumulation of mitochondrial DNA fragments may progressively change the nuclear information content and thereby cause aging. This proposal can be tested experimentally.

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Repair of pyrimidine dimers in nuclear and mitochondrial DNA of yeast irradiated with low doses of ultraviolet light

Cited by 151 publications

References 28 publications

Regulation of CDC9, the Saccharomyces cerevisiae gene that encodes DNA ligase.

Regulation of CDC9, the Saccharomyces cerevisiae gene that encodes DNA ligase.

The fate of 8-methoxypsoralen photoinduced crosslinks in nuclear and mitochondrial yeast DNA: comparison of wild-type and repair-deficient strains.

Do mitochondrial DNA fragments promote cancer and aging?

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