[Myocardium of mdx mice contains factor(s) that damage DNA structure and retard DNA reparation after gamma-irradiation (experiences in modeling system)]. / Miokard myshei mdx soderzhit faktor(y), kotorye povrezhdaiut strukturu i, vozmozhno, tormoziat reparatsiiu DNK posle gamma-oblucheniia (opyty v model'noi sisteme).

We studied the action of saline extracts of ventricle myocard (EM) of C57BL and mdx mice on DNA structure and repair of one-strand breaks of DNA in a modelling system. The system involves DNA repair in E. coli WP2 cells after gamma-irradiation. Using standard technique, DNA reparation was estimated on measuring the speed of E. coli DNA sedimentation in alkaline sucrose gradients. It was shown, that EM of C57BL or mdx mice exerted no influence on DNA repair, which was completely declined within 60 min with EM present in the growth medium of permeabilized E. coli. Addition of C57BL mice EM into lytic solution does not accelerate DNA sedimentation of nonirradiated E. coli. At the same time, EM of mdx mice sharply accelerates DNA sedimentation of nonirradiated E. coli reducing DNA molecular weight from 200 x 10(6) to 135 x 10(6) Da. At entering in the lytic solution the EM of mdx mice also slows down E. coli DNA repair after gamma-irradiation. It is supposed, that EM of mdx mice may contain a factor(s) damaging DNA in the E. coli lysate and presumably slowing down DNA reparation after gamma-irradiation. Russian Foundation of Basic Research Grants 99-04-49390, 02-04-49870 and 00-04-49390.

[Radioadaptive enhancement of the repair of UV-induced postreplication gaps in Escherichia coli cells deficient in DNA repair]. / Radioadaptivnoe usilenie reparatsii UF-indutsirovannykh postreplikativnykh probelov v kletkakh Escherichia coli, defektnykh po reparatsii DNK.

In UV-irradiated E. coli WP2 uvrA, deficient in excision repair of DNA with pyrimidine dimers, gamma-irradiation in low doses (radioadaptation) before UV-irradiation leads to the intensification of postreplication repair of DNA. This process in WP2 uvrA polA and uvrA lexA mutants is less than in WP2 uvrA cells, but in WP2 uvrA recA both postreplication repair and its radioadaptive intensification are absent. In E. coli AB1157 excising pyrimidine dimers the radioadaptive intensification of postreplication repair of DNA is expressed almost to the same extent as in WP2 uvrA. In GW2100 umuC mutant, deficient in DNA polymerase V, postreplication repair of DNA is expressed, but its radioadaptive intensification is absent, while in AB2463 recA13 both postreplication repair of DNA and radioadaptive intensification of postreplication repair of DNA are absent. The above data suggest that DNA polymerase I and LexA protein are needed for radioadaptive intensification of postreplication repair of DNA in uvrA strain, and DNA polymerase V is needed for radioadaptive intensification in E. coli AB1157, and that RecA protein is required for postreplication repair and radioadaptive intensification of postreplication repair of DNA.

[ Effect of gamma radiation, cis-diamminedichloroplatinum and its derivates on the Escherichia coli cell survival and potentiality for adaptive response]. / Vyzhivaemost' i vozmozhnost' adaptivnogo rosta u Escherichia coli pri deistvii gamma-oblucheniia, cis-diaminodikhlorplatiny i nekotorykh ee proizvodnykh.

The sensitivity to the lethal effect of gamma-rays, cis- and trans-diamminedichloroplatinum (DDP), cis- and trans-iminoethers of DDP (IE) was compared in two groups of E. coli--K12 and B. In all experiments, cells of wild types appeared to be most resistant to these agents. gamma-Resistant and gamma-sensitivity/hypersensitive strains occupy an intermediate position according to their sensitivity to cis-DDP derivatives. In almost all the cases, both single and especially double mutants defective for the systems of nucleotide excision repair, recombination repair, and inducible SOS-repair are most sensitive to DDP derivatives. The data obtained show that in E. coli the repair of lethal lesions after cis-DDP action is more complicated than after gamma-irradiation. Of DDP derivatives cis-DDP is most effective, while trans-DDP is less effective, and cis- and trans-IE are considerably less effective, respectively. It is shown that the effects of ionizing radiation in low doses (more than 10 different regimes), or of treatment with cis-DDP in low concentrations do not change the survival of E. coli after their respective effects in high doses. In other words, under the effect of ionizing radiation and cis-DDP no adaptive response for the lethal action was found in E. coli.

[Radioadaptive enhancement of the repair of UV-induced postreplication gaps in Escherichia coli DNA]. / Radioadaptivnoe usilenie reparatsii UF-indutsirovannykh postreplikativnykh probelov v kletkakh Escherichia coli.

Postreplication DNA repair (PRR) in UV-irradiated Escherichia coli WP2 uvrA (tryptophan-dependent strain) and K12 AB1886 uvrA6 pre-irradiated by gamma-rays in low doses (radioadaptation, the first stress effect) has been investigated. PRR was found to be more effective after incubation in the growth medium (for 45-60 min) than in non-radioadapted cells: the repair of postreplication gaps increased by 6-15%. If cells of WP2 uvrA strain were incubated after UV-irradiation in media lacking tryptophan or casamin acids (the second stress effect), PRR was seen to increase as early as within 15 min of incubation and it is more effective than at the first stress. After a 30-60 min incubation the double stress effect leads to an increase in postreplication gap repair by 23-45%. In this case almost all the gaps prove to be repaired. The second stress alone exerts no influence on PPR efficiency. It is supposed that a preliminary radioadaptation may stimulate synthesis of a protein (proteins) of the SOS-response (presumably DNA polymerase V). The second stress effect apparently induces synthesis of an unknown factor (or depreesses synthesis of a MmrA-like protein), and this in cooperation with a protein newly synthesized during radioadaptation significantly increases the efficiency of PPR.

[Non-mutagenic and mutagenic post-replicative DNA repair in prokaryotic and eukaryotic cells]. / Nemutagennaia i mutagennaia postreplikativnaia reparatsiia DNK v kletkakh prokariot i éukariot.

The review is devoted to mechanisms of repair gaps in DNA daughter strand, formed during the stall of moving replication forks and restart of replication in cells after the action of DNA damaging agents (predominantly--UV light). The repair of daughter DNA, or postreplication DNA repair (PRR), is realized by error-free (non-mutagenic) and error-prone (mutagenic) pathways. The former is a recombination repair, or recombination between two sister duplexes. By this way the major part of postreplication gaps is eliminated. The second way is related with the induction of SOS-response. In Escherichia coli cells mutagenic SOS-response is realized by proteins RecA, UmuD, UmuC, DNA-polymerase III holoenzyme and others. In E. coli some mutagenic enzymes--DNA-polymerase IV (the product of dinB gene) and DNA-polymerase V (the product of umuDC genes) have been recently discovered. In Saccharomyces cerevisiae cells postreplicative translesion synthesis is realized by newly discovered enzymes deoxycytidilmonophosphatetransferase (encoded by REV1 gene), DNA-polymerase zeta (encoded by REV3 gene), DNA-polymerase eta (encoded by RAD30 gene). All the three enzymes share a great homology with UmuC enzyme of E. coli. DNA polymerase eta correctly inserts adenine residues in the daughter strand opposite noncoded thymine residues in cyclobutane pyrimidine dimer. Based on RAD6 gene of S. cerevisiae, human cells hREV1, hREV3 and hRAD30A have been obtained to encode, respectively, deoxycytidiltransferase, DNA-polymerase zeta and DNA-polymerase eta. It has been shown that the defect of PRR DNA in xeroderma pigmentosum variant is associated with DNA-polymerase eta deficiency. This defect is corrected by the extract of intact HeLa cells. The importance of newly discovered enzymes in the system of mechanisms of DNA repair and replication is discussed.

[Defect of preferential repair of gamma-ray-induced single-strand breaks in transcribed DNA in ataxia-telangiectasia cells]. / Defekt preimushchestvennoi reparatsii gamma-indutsirovannykh odnonitevykh razryvov b transkribiruemoi DNK pri ataksii-teleangiéktazii.

Transcriptionally activity-dependent heterogeneity of gamma-induced DNA single-strand break repair in ataxia-telangiectasia cells has been investigated. It is found that in AT cells no increased induction of damage in the c-myc gene compares with normal human fibroblasts. At the same time an evident defect of preferential accelerated repair of single-strand breaks in the c-myc gene was observed. DNA single-strand breaks repair in human satellite III and total DNA single-strand breaks in c-myc gene in AT cells correlate with increased radiosensitivity of cells.

[Defect of preferential repair of gamma-ray-induced single-strand breaks in transcribed and non-transcribed DNA in Cockayne syndrome cells]. / Defekt preimushchestvennoi reparatsii gamma-indutsirovanny odnonitevykh razryvov v transkribiruemoi i netranskribiruemoi DNK pri sindrome Kokeina.

The repair of gamma-ray-induced DNA single-strand breaks in transcribed (protooncogene c-myc) and non-transcribed (human satellite III) DNA of normal human fibroblasts and fibroblasts obtained from a patient with Cockayne's syndrome (CS) has been investigated. A method of alkaline sucrose sedimentation was applied besides the Southern hybridization of 32P-DNA, containing sequences analysed with total 3H-DNA distributed through sucrose gradient fractions. No increase in the induction of DNA single-strand breaks was found in gamma-irradiated CS fibroblasts, compared to normal human fibroblasts. At the same time, an evident defect in the preferential repair of single-strand breaks in c-myc gene was observed.

[Relationship between transcription and repair of radioinduced DNA damage]. / Sviaz' transkriptsii i reparatsii radioindustiruemykh povrezhdenii DNK.

The DNA repair is occurred on genome level with different rates. This rates are depend on a transcription activity of various genome sequences. The repair rates are low in non-transcribed genes and DNA sequences, more higher in transcribed genes and the highest in actively transcribed strands of active genes. Such classification could be applied to the repair of UV-induced cyclobutane pyrimidine dimers and for other (but not for all) DNA lesions. This observation has become a basement of such important findings as involvement of transcription into repair or existence of transcription-coupling repair factors (i.e. TFIIH). Thymine glycoles which are appear under ionizing radiation exposure, are repaired preferentially in transcribed DNA. In present reviewer we observe the preferential repair of ionizing radiation-induced single strand breaks (SSBs) in transcribed DNA of human cells. Discontinuous distribution of DNA repair along hole genome has a grate role in biological processes. The data, obtained on cells from patient with rare hereditary disease Cockayne syndrome have shown that there is the defect of preferential repair of pyrimidine dimers and ionizing radiation-induced thymine glycols and SSBs in transcriptionally active DNA sequences. In case of another rare hereditary disease-ataxia telangiectasia the defect of preferential repair of ionizing radiation-indiced SSBs was observed. The defect of preferential repair of radio-induced damages in AT and CS cells can explain such fishers of this diseases as high sensitivity to ionizing radiation.

[The repair of DNA single-stranded breaks and degradation under the action of novobiocin in gamma-irradiated HeLa cells]. / Reparatsiia odnonitevykh razryvov i degredatsiia DNK pri deistvii novobiotsina v gamma-obluchennykh kletkakh HeLa.

A method of sedimentation in alkaline sucrose gradients was used to study repair of gamma-induced DNA single strand breaks (SSB) and DNA degradation in HeLa cells treated with novobiocin (Nb), an inhibitor of topoisomerase II. After irradiation in a dose of 150 Gr, Nb in a concentration of 1 mM does not affect the effectivity of SSB repair and DNA molecular mass in the irradiated cells treated with Nb for 60-180 min before irradiation. Besides, it does not lead to additional DNA degradation in cells treated with Nb for 60-180 min before gamma-rays, as well as following a postirradiation incubation during 60-180 min. Nb in a concentration of 4 mM, much exceeding the Nb concentration when DNA synthesis and cell transit through the cycle are inhibited, causes the following changes. It does not affect DNA molecular mass in non-irradiated cells, inhibits repair of DNA SSB, causes partial DNA degradation, if cells are treated for 60-180 min before gamma-rays and during the following postirradiation incubation (60-180 min). Taking into account the Nb-mediated DNA degradation, the inhibition of DNA repair by Nb appears not significant. Since in a concentration, which inhibits topoisomerase II, Nb does not affect repair of gamma-induced DNA SSB, one may assume the lack of involvement of topoisomerase II into repair of these DNA lesions. Inhibition of DNA repair by 4 mM Nb may result from its effect on the number of proteins, including reparative DNA polymerase, rather than from a selective effect on topoisomerase II.

[The suppression of the repair of radio-induced DNA damage in Escherichia coli cells by indazolin derivatives and proksifein]. / Podavlenie reparatsii radioindutsiruemykh povrezhdenii DNK v kletkakh Escherichia coli proizvodnymi indazolina i proksifeinom.

A study was made of the postradiation effect of five indasoline derivatives and proxyfeine on the survival rate and repair of DNA single-strand breaks in E. coli exposed to gamma-irradiation. Some indasoline derivatives (three substances) and proxyfeine added in postradiation medium in nontoxic concentrations decreased the survival rate of radioresistant strains WP2 hcr+, Hr30 and Hs30, but do not influence survival rate of radiosensitive mutant Bs-1. These substances inhibit the repair of DNA single-strand breaks in E. coli WP2 hcr+. Substances, which do not inhibit the survival rate of radioresistant strains, do not inhibit the repair of breaks. Proxyfeine in non-toxic concentrations in non-irradiated cells induces DNA degradation. Indazoline derivatives do not induce DNA degradation. Data presented suggest that indasolines are new class inhibitors of DNA repair. It is possible that proxyfeine is too an inhibitor of DNA repair.

[The repair of UV-induced postreplication DNA gaps in Escherichia coli cells adapted to methylmethane sulfonate and ethylmethane sulfonate]. / Reparatsiia UF-indutsirovannykh postreplikativnykh probelov DNK v kletkakh Escherichia coli, adaptirovannykh k metilmetansul'fonatu i étilmetansul'fonatu.

The survival (only after the adaptation to methylmethane sulfonate, MMS) and repair of DNA postreplication gaps in UV-irradiated Escherichia coli, adapted to MMS (20 mkg/ml for 3 h) and ethylmethane sulfonate (EMS, 100 mkg/ml for 3 h), have been investigated. The survival of MMS-adapted bacteria of wild strains B/r and K12 AB1157 somewhat increased, whereas the survival of AB1886 uvrA mutant, which unlike the wild type bacteria is unable to excise cyclobutane pyrimidine dimers, was seen to decrease. The repair of postreplicative gaps in MMS-adapted bacteria correlates qualitatively with changes in survival: in B/r and AB1157 strains the repair is somewhat more effective (10-15%), while in AB1886 uvrA mutant significantly slower (near 30%) than in non-adapted bacteria. Similar changes of postreplicative repair (PRR) of DNA are observed in AB1157 and AB1886 uvrA strains adapted to EMS. It is suggested that the decreased efficiency of PRR in bacteria AB1886 uvrA, adapted to alkylating agent, may be due to the interference between the two inducible repair processes: adaptive response and SOS response. The latter process is involved in the repair of some part of postreplicative gaps of DNA. Different results of PRR of DNA in bacteria of wild types, adapted to MMS and EMS, may be associated with the intrinsic PRR in uvr+ strains. Due to this process in uvr+ bacteria SOS component of PRR of DNA is not formed. It is suggested that PRR in uvr+ bacteria adapted to alkylating agents is accelerated by enzymes of adaptive response in the absence of antagonism between the SOS response and the adaptive response.

[The repair of gamma-induced single-stranded breaks in the transcribed and nontranscribed DNA of HeLa cells]. / Reparatsiia gamma-indutsirovannykh odnonitevykh razryvov v transkribiruemoi i netranskribiruemoi DNK kletok HeLa.

The repair of gamma-ray-induced DNA single-strand breaks (SSB) in transcribed (Alu-enriched DNA, proto-oncogene c-myc) and non-transcribed (human satellite III) DNA of HeLa cells has been investigated. A special methodical approach has been developed. The method involved alkaline sucrose sedimentation followed by Southern hybridization in situ of 32P labelled plasmids (probes) containing sequences analysed with total DNA distributed through sucrose gradient fractions. The degree of the probes hybridization with cellular DNA was the criteria of the damage and that of DNA repair. The induction of DNA SSB after irradiation (100 Gy) in Alu-enriched DNA and c-myc gene was shown to be 1.3-1.4 time more often while than in satellite DNA, and 1.4 time lower compared to that in total DNA. The rate of DNA repair was different: the most part of lesions was eliminated in the first 10-20 minutes in all cases. For this time 60-67, 50-66, 35-50 and 45-50% DNA SSB were eliminated from transcribed DNA (c-myc, Alu), non-transcribed DNA (satellite III) and total DNA, respectively. Thus, the preferable (fast) repair of gamma-ray-induced DNA SSB takes place in transcribed DNA compared to that in non-transcribed DNA of HeLa cells.

[Survival and the repair of single-stranded DNA breaks in gamma-irradiated Escherichia coli cells adapted to methylmethane sulfonate]. / Vyzhivaemost' i reparatsiia odnonitevykh razryvov DNK v gamma-obluchennykh kletkakh Escherichia coli pri adaptatsii k metilmetansul'fonatu.

The survival and repair of single-strand breaks of DNA in gamma-ray-irradiated E. coli adapted to MMS (20 mkg/ml during 3 hours) have been investigated. It is shown that the survival of adapted bacteria of radioresistant strains B/r, H/r30, AB1157 and W3110 pol+ increases with DMF (dose modification factor) ranging within 1.4-1.8 and in radiosensitive strains Bs-1, AB1157 recA13 and AB1157 lexA3 with DMF ranging within 1.3-1.4, and does not change in strains with mutation in polA gene P3478 polA1 and 016 res-3. There is no increase in radioresistance during the adaptation to MMS under the action of the protein synthesis inhibitor chloramphenicol. The increase in radioresistance during the adaptation to MMS correlates with the acceleration of repair of gamma-ray-induced single-strand breaks in the radioresistant strains B/r and W3110 pol+ and with the appearance of the ability to repair some part of DNA single-strand breaks in the mutant Bs-1, which beyond the adaptation to MMS does not repair these damages. The incomplete reparability of DNA single-strand breaks in P3478 polA1 strain cells, both adapted and non-adapted to MMS, is equal.

[The adaptive response to mitomycin C exposure in the hyper-radioresistant mutant Escherichia coli Gamr444]. / Adaptivnyi otvet na vozdeistvie mitomitsinom C u giperradiorezistentnogo mutanta Escherichia coli Gamr444.

Adaptive response to mitomycin C (MC) (lethal effect and recovery of molecular mass of DNA) in hyper-radioresistant mutant Escherichia coli Gamr444 have been investigated. This mutant is more resistant to MC than parent strain E. coli K12 AB1157. Adaptation of Gamr444 mutant to MC in nonlethal concentrations increases its resistance to MC in lethal concentrations with dose modification factor (DMF) 2.4 at the LD90 level. During the adaptation of this mutant to methyl-methane sulfonate (MMS) its resistance to this agent increases with DMF by 2.2 and resistance to MC with DMF by 1.5 times. During the adaptation of Gamr444 mutant to MC its resistance to MMS increases with DMF by 1.5 times. Adaptive response to MC abolishes by chloroamphenicol treatment during the adaptation. Adaptive response to nitrogen mustard (HN2) in E. coli Gamr444 is absent (HN2 induces cross-links in DNA as MC). Degradation of DNA following the formation of cross-links in DNA takes place. Adaptation to MC in Gamr444 mutant leads to restoration of DNA molecular mass which is more quicker than in the case without adaptation. Adaptive restoration of DNA molecular mass after the MC treatment is absent in E. coli K12 AB1157. The repair of cross-links in DNA after the treatment of HN2 in Gamr444 mutant takes place with equal rate both in the case of adaptation to HN2 and in the case without adaptation. It is proposed, that under the treatment of MC in E. coli Gamr444 the ada-alkA-dependent adaptive response takes place. This adaptive response is connected with alkylation of O6-guanine and elimination of the product by O6-alkyl-DNA-alkyltransferase. Partial recA-dependency of the adaptive response to MC allows to suggest the participation of another inducible system. The nature of this system is unknown.

[The restoration by Escherichia coli RecA protein of the survival of gamma-irradiated HeLa cells reduced by the DNA repair inhibitors caffeine and 3-aminobenzamide]. / Vosstanovlenie RecA-belkom Escherichia coli vyzhivaemosti gamma-obluchennykh kletok HeLa, snizhennoi ingibitorami reparatsii DNK kofeinom i 3-aminobenzamidom.

It is confirmed that inhibitors of DNA repair caffeine and 3-aminobenzamide decrease the survival of gamma-irradiated HeLa cells. It is shown that the decreased survival of irradiated cells is reversed when Escherichia coli RecA protein is introduced into cell nucleases with the aid of liposomes. This effect is more expressed in caffeine-treated (before or after irradiation) than in 3-aminobenzamide-treated (before irradiation) cells. It is suggested that E. coli 38 kD RecA protein may compensate the function of HeLa RecA-like protein, inhibited by DNA repair inhibitors, which is necessary for the repair of single-strand breaks and double-strand breaks of DNA.

[The relationship between the radiosensitivity of DNA replicative synthesis and the formation of sister chromatid exchanges]. / K voprosu o sviazi mezhdu radiochuvstvitel'nost'iu replikativnogo sinteza DNK i obrazovaniem sestrinskikh khromatidnykh obmenov.

It has been found that irradiation in doses 0.5-2.0 Gy does not enhance the frequency of sister chromatid exchanges in cells of patients with Down's syndrome and ataxia-telangiectasia compared to the normal cells. In the case of ataxia, this phenomenon was accompanied with radioresistant replicative DNA synthesis, whereas in two cases of Down's syndrome the replicative DNA synthesis was found to be as radiosensitive as in the norm. According to these data, the mechanism of sister chromatid exchanges proposed in our previous publication (Pleskach et al., 1988) seems to be rather doubtful.

[The regulation of DNA repair in mammalian cells. I. The repair of DNA radiation damages in Swiss 3T6 mouse cells under the action of the epidermal growth factor and insulin]. / Reguliatsiia reparatsii DNK v kletkakh mlekopitaiushchikh. I. Reparatsiia radiatsionnykh povrezhdenii DNK v myshinykh kletkakh Swiss 3T6 pri deistvii épidermal'nogo faktora rosta i insulina.

Methods of centrifugation in alkaline sucrose gradients as well as alkaline and neutral elution on filters were used to show a significant reduction in the rate of both single- and double-strand DNA breaks in the quiescent mouse Swiss 3T6 cell culture as compared to the proliferating one. The low efficiency of repair of single-strand DNA breaks in quiescent cells may result from a nearly complete absence of the fast repair of DNA lesions during the first minutes of postradiation incubation. The epidermal growth factor in combination with insulin (no other serum component present) leads to a recovery of the repair process. The stimulating effect of mitogens on the repair of both single- and double-strand DNA breaks allows to suggest that similar factors may be responsible for these recovery processes.