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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The GC and AT fractions (GC content is 55.2 and 36.2 mole %, respectively) were isolated from wheat germ DNA by the thermal fractionation method (sequential thermal DNA denaturation followed by separation of denatured and undenatured DNA molecules by hydroxyapatitie chromatography). The amount of each of the two fractions isolated corresponds to about 25% of the total DNA. The 5-methylcytosine (m5C) content in the GC fraction (9.2 mole %) is 4.6 times higher than in the AT fraction. The DNA fractions isolated are very different in the level of methylation of cytosine residues (m5C/C+m5C ratio differs 3 times), in the amount of respective pyrimidine isostichs and in the renaturation kinetics. In contrast to the AT fraction, in the GC fraction the amount of dipyrimidine isostichs is higher than monopyrimidine ones. The AT and GC fractions isolated contain unique, moderately and highly reiterated nucleotide sequences. About 90% of the GC fraction is represented by reiterated sequences. The isolated (from the GC fraction) highly reiterated sequences (GC fraction I, Cot = 2.8 X 10(-2)) are very similar to the original GC fraction in the GC and m5C contents as well as in the amount of m5C in the respective pyrimidine isostichs. GC fraction I differs from the total GC fraction in a lower pyrimidine clustering degree. In total DNA and in GC and AT fractions m5C is found in mono- (34-40% of total m5C), di-(26-30%) and in all longer pyrimidine isostichs. It is suggested that in plants there exist many types of DNA sequences to be methylated as well as many respective DNA methylases.
Mol Biol (Mosk)
PMID:[Character of the methylation and reassociation of wheat DNA fractions differing in their nucleotide composition]. 68 93

We have studied a number of condensation reactions involving ImpU, ImpT, ImpC, ImpA, ImpG, ImpUgG and ImpCpA as activated nucleotide donors and a variety of homo- and hetero-polynucleotides as templates. We did not not obtain any evidence of a template effect with ImpU and ImpT, but observed some condensation of ImpC with GpG on appropriate templates. ImpA and ImpG take part in a number of more or less efficient template-directed reactions, as do ImpUpG and ImpCpA. Our results suggest that, on the primitive Earth, pyrimidine nucleotides could most easily have been incorporated into polymers as constituents of short oligomers, which contained one or more purine nucleotide. The linkage of the product depends strongly on the nature of the substrates; the percentage of the natural 3'-5'-linkage was, in some cases, less than 10% and, in others, as high as 70%. Wobble-pairing was often very effective in promoting condensations, suggesting that transition mutations would have been very frequent in prebiotic polynucleotide replication.
J Mol Evol 1978 Dec 29
PMID:Heteropolynucleotides as templates for non-enzymatic polymerizations. 73 54

The filling of about one third of postreplication DNA gaps in u.v.-irradiated Micrococcus luteus ATCC 4698 is blocked by chloramphenicol (CA) added just before irradiation. Addition of CA 15 min after u.v.-irradiation does not prevent the complete repair of the gaps. U.v.-sensitive M. luteus mutants (ML 6 and ML 15) are identified as defective in different steps of inducible postreplication DNA repair (PRR). PRR in unexcising M. luteus strain G7 is accompanied by the transfer of about 20% of pyrimidine dimers from parental to daughter DNA strands, which indicates the existance of recombinational pathway of PRR. Recombinational PRR in M. luteus is not inhibited by CA.
Mol Biol Rep 1978 Oct 16
PMID:Effects of chloramphenicol on the postreplication repair and sister recombinational DNA exchanges in ultraviolet-irradiated Micrococcus luteus. 73 81

Pyrimidine sequences of DNA from three fishes: shark, protopterus and perch have been studied. These data together with the evidence from the literature were used to support earlier conclusions that dipnoi and cartilagenous fishes should be distinguished as independent classes. The clustering index, beta, and the total molar percentage of long pyrimidine oligonucleotides (Z) containing greater than or equal to 8 nucleotides--a new parameter offered by us--have been used in comparative investigation of DNAs. The new parameter has permitted to obtain a higher resolution in the analysis of our own and literature data on DNA pyrimidine clusters in fishes. Investigation of pyrimidine clusters and of the base composition of individual isoplits of these clusters using statistical analysis showed that DNA from shark, protopterus, sturgeon and perch significantly differ by many features. Significant differences between these DNAs were found also in the base composition. Thus, new evidence for distinguishing cartilagenous fishes and dipnoi as independent classes have been received.
Mol Biol (Mosk)
PMID:[A comparative characteristic of DNA pyrimidine sequences of shark, protopterus and perch]. 75 76

We prove that the sequence of purine and pyrimidine blocks can be restored for circular nucleic acids if molecular weight distributions of fragments of various stages of hydrolysis are known. Hydrolysis of nucleic acid is considered as a progressive fragmentation of a "ciphering", an arbitrary circular polymer, monomers of which have weights from 1 to 6 (corresponding to the real number of purines or pyrimidines in the block), while the site of fragmentation is selected at random. The hydrolysis of circular RNA under the action of pancreatic RNase proceeds in accordance with the model of ciphering. Heuristic method for restoration of the monomer sequence in the ciphering based upon some characteristics of molecular weight distributions (such as Sj(m)-number of the fragments with the weight m containing j unbroken bonds) is considered. Uniqueness of restoration of the monomers sequence of the ciphering based upon known set [Sj(m)] is proved.
Mol Biol (Mosk)
PMID:[Kinetic method for the determination of sequences of purine and pyrimidine blocks for circular nucleic acids]. 75 79

Ultraviolet (UV) mutagenesis in E. coli is associated with a UV-inducible type of error-prone postreplication repair ("SOS" repair) which, in tif-1 strains, is thermo-inducible in coordination with other recA+ lexA+-dependent inducible functions, including filamentous growth. Mutants of E. coli B/r tif-1 strains have been isolated which retain thermoinducibility of SOS repair activity, but lack the thermosensitivity caused by filamentous growth at 42 degrees C. These strains have been used to determine: the kinetics of decay at 30 degrees C of thermally induced ability to enhance UV mutagenesis; the kinetics of thermal enhancement of spontaneous and UV-induced mutability at 42 degrees C, and the kinetics of decay at 30 degrees C of susceptibility to thermal enhancement of spontaneous and UV-induced mutability. Mutations from tryptophane requirement to prototrophy (Trp- to Trp+) were scored. UV doses were 0.2 J/M2 for excision repair-deficient (Uvr-) and 2J/m2 for Uvr+ strains. The results support the following conclusions. 1) thermally induced SOS repair activity decays at 30 degrees C to about 25% of its maximum level in 45 min, and is no longer detectable after 90 min. 2) Thermal enhancement of UV mutability occurs at sites produced primarily (perhaps exclusively) before completion of the first post-irradiation cell division. 3) UV-induced sites susceptible to thermally induced SOS repair are stable at 30 degrees C in cells not containing the error-prone repair system, and are refractory to constitutive error-free repair for at least 2-3 hours. 4) UV produces a potentially mutagenic type of photoproduct in DNA which can, without interacting with another UV lesion, provide a site susceptible to SOS repair, but which is not a sufficient signal for SOS induction. 5) 50-70% of the SOS-mutable SOS-noninducing UV photoproducts are photoreversible pyrimidine dimers. The results are discussed in relation to current models of UV mutagenesis and induction of UV-inducible functions.
Mol Gen Genet 1975 Dec 29
PMID:Persistence and decay of thermoinducible error-prone repair activity in nonfilamentous derivatives of tif-1, Escherichia coli B/r: the timing of some critical events in ultraviolet mutagenesis. 76 39

When DNA of phage chiX174 or phage f1 is used as a template after exposure to ultraviolet radiation, the conversion of single-stranded DNA to replicative form by cell-free extracts of Escherichia coli is inhibited. The extend of synthesis is proportional to the distance of a pyrimidine dimer from a specific origin of replication as calculated from the random location of dimers at various UV doses. The results therefore indicate that the initiation of DNA synthesis on these phage DNAs occurs normally at a specific site, and that chain elongation is blocked when replication reaches a photo product in the template. Reinitiation of DNA synthesis distal to the lesion does not occur.
Mol Gen Genet 1976 Dec 22
PMID:Effect of ultraviolet irradiation of bacteriophage f1 DNA on its conversion to replicative form by extracts of Escherichia coli. 79 53

The combined action of 8-methoxypsoralen (8-MOP) and light with lambda greater than 310 nm on bacteriophages and bacteria results in the formation of the following two types of photo-products in the DNA: monoadducts, in which 8-MOP is covalently bound to a pyrimidine base, and diadducts or cross links, in which the 8-MOP is covalently bound to two pyrimidines from complementary strands. The method of repeated irradiation has been proposed for analyzing the degree of lethality of the photoproducts in DNA. According to this method, the preparation is freed of free 8-MOP molecules after the first irradiation and then irradiated for a second time. In this case the monoadducts are converted into cross linkages between the strands. Approximately 3-10(-9) cross links/Dalton-min form in Escherichia coli DNA during the first irradiation. The rate of the formation of cross links drops by a factor of about 2 during the repeated irradiation. It has been shown that the 8-MOP monoadducts are repaired by the uvr system just as efficiently as are lethal photoproducts of the cyclobutane pyrimidine dimer type. Lethal cross linkages in bacteria and phages are repaired by the joint action of the uvr, recA, and lex systems. A scheme has been proposed for the repair of cross linkages in one genome by these systems. The photoreactivating enzyme is inactive on DNA subjected to the combined action of 8-MOP and light. The kinetics of the repair of monadducts in bacteria and phages with various defects in the repair systems have been studied. It has been shown that the products of genes recA and lex take part in the repair process according to an excision-resynthesis method. The use of the method of repeated irradiation with 8-MOP as an express method for detecting repair systems of the uvr type in cells has been proposed.
Mol Biol (Mosk)
PMID:Repair of 8-methoxypsoralen monoadducts and diadducts in bacteriophages and bacteria. 79 58

Bacillus subtilis competent cells were transfected with SPP1 heteroduplices having pyrimidine dimers in one of the strands. The data obtained reveal that excision repair of the pyrimidine dimers influences the ratio of wild type versus mutant progeny observed in "normal" heteroduplex transfection. With increased exposure of one strand to UV dose the percentage of infective centers having the unirradiated strand genotype shows an increase. A comparison of the transfection data in her+ and her- host excludes asymmetric replication as the cause of the observed changes in the conversion pattern. The data can be explained on the basis of a dimer induced co-excision of the mismatched region. In addition transfection data from wild type/deletion mutant heteroduplices where the strand of mutant origin was irradiated exclude the possibility of the wild type loop being excised during uptake.
Mol Gen Genet 1975 Aug 05
PMID:Transfection with heteroduplex SPP1 DNA: a pyrimidine dimer induced influence on the conversion pattern. 80 63

Two allelic auxotrophic mutants at a locus close to the bw locus (2-104.5) of Drosophila melanogaster are described. The mutants respond to dietary ribonucleosides (uridine, cytidine, adenosine, guanosine and inosine) but less well to bases or pyrimidine precursors. This phenotype is unique to these mutants. We suggest that the mutants are defective in phosphoribosyl pyrophosphate biosynthesis.
Mol Gen Genet 1976 Aug 10
PMID:Nucleoside auxotrophy in Drosophila: an autosomal locus yielding mutants supplementable by purine and pyrimidine ribonucleosides. 82 79


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