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1.
Inhibitors of DNA synthesis (aphidicolin and araC/HU) prevent the recovery of RNA synthesis after UV-irradiation 总被引:4,自引:0,他引:4
L V Mayne 《Mutation research》1984,131(5-6):187-191
UV-irradiation causes an immediate depression in the rate of RNA synthesis in human skin fibroblasts. RNA synthesis rates recover to greater than or equal to 90% of unirradiated levels within 90 min in normal cells. This recovery can be prevented by incubating the cells after irradiation with araC/HU or aphidicolin, potent inhibitors of DNA replication and excision repair. The effect of these inhibitors on the recovery of RNA synthesis can also be observed in non-dividing cells; it is thus independent of their effects on DNA replication. 相似文献
2.
3.
L Vaughan M Mendler S Huber P Bruckner K H Winterhalter M I Irwin R Mayne 《The Journal of cell biology》1988,106(3):991-997
It has recently become apparent that collagen fibrils may be composed of more than one kind of macromolecule. To explore this possibility, we developed a procedure to purify fibril fragments from 17-d embryonic chicken sternal cartilage. The fibril population obtained shows, after negative staining, a uniformity in the banding pattern and diameter similar to the fibrils in situ. Pepsin digestion of this fibril preparation releases collagen types II, IX, and XI in the proportion of 8:1:1. Rotary shadowing of the fibrils reveals a d-periodic distribution of 35-40-nm long projections, each capped with a globular domain, which resemble in form and dimensions the aminoterminal globular and collagenous domains, NC4 and COL3, of type IX collagen. The monoclonal antibody (4D6) specific for an epitope close to the amino terminal of the COL3 domain of type IX collagen bound to these projections, thus confirming their identity. Type IX collagen is therefore distributed in a regular d-periodic arrangement along cartilage fibrils, with the chondroitin sulfate chain of type IX collagen in intimate contact with the fibril. 相似文献
4.
Thomas F. Linsenmayer Anita Mentzer Michael H. Irwin N. Keith Waldrep Richard Mayne 《Experimental cell research》1986,165(2):518-529
Two monoclonal antibodies have been characterized as being against avian type VI collagen. By competition ELISA, the antibodies bound to the native type VI collagen molecule but not to its separated chains or to any of the other native collagen types tested. By rotary shadowing analysis of complexes of antibody-type VI collagen monomers, one of the antibodies (VI-EC6) has been shown to bind to a site in the triple helical domain of the molecule. The site at which this antibody binds to the dimeric form of type VI collagen is consistent with the previously proposed model for a supramolecular organization of the molecule (Furthmayr et al., Biochem j 211 (1983) 303) in which the monomers are arranged in an antiparallel, slightly staggered overlap. Immunofluorescence analyses of sections of chicken eyes and skeletal muscle demonstrate that type VI collagen is a major component of most stromal matrices. 相似文献
5.
Efficient immortalization and morphological transformation of human fibroblasts by transfection with SV40 DNA linked to a dominant marker 总被引:10,自引:0,他引:10
Lynne V. Mayne Anne Priestley Michael R. James Julian F. Burke 《Experimental cell research》1986,162(2):530-538
Immortal cell lines are essential for genetic and biochemical studies. Unlike rodent cells, which will form continuously growing cultures either spontaneously or after infection with an oncogenic virus (e.g., Simian Virus 40 (SV40)), human cells fail to form continuous cell lines spontaneously and in only rare cases from cell lines after oncogenic virus infection. We have used a plasmid (pSV3gpt) containing both the SV40 early region encoding T antigen and the bacterial gene xanthine-guanine phosphoribosyl transferase (gpt) to achieve high efficiency morphological transformation and immortalization of primary human skin fibroblasts. Transfection of this plasmid into primary human skin fibroblasts derived from a normal individual, two Cockayne's syndrome patients, and an immuno-deficient patient and selection for the gpt gene resulted in an altered cell morphology and growth properties characteristic of previously described SV40-transformed cells. Transfected cultures subsequently senesced, entered crisis and in each case formed a rapidly growing culture. The high efficiency of immunortalization described here (four out of four cell strains) is in contrast to previously described procedures utilizing focal overgrowth. We suggest that the use of a dominant selectable marker linked to the SV40 early region increases the probability of establishing an immortal human cell line. 相似文献
6.
The effects of mispair and nonpair correction in hybrid DNA on base ratios (G + C content) and total amounts of DNA 总被引:1,自引:0,他引:1
Base ratios and total DNA amounts can vary substantially between and within
higher taxa and genera, and even within species. Gene conversion is one of
several mechanisms that could cause such changes. For base substitutions,
disparity in conversion direction is accompanied by an equivalent disparity
in base ratio at the heterozygous site. Disparity in the direction of gene
conversion at meiosis is common and can be extreme. For transitions (which
give purine [R]/pyrimidine [Y] mispairs) and for transversions giving
unlike R/R and Y/Y mispairs in hybrid DNA, this disparity could give slow
but systematic changes in G + C percentage. For transversions giving like
R/R and Y/Y mispairs, it could change AT/TA and CG/GC ratios. From the
extent of correction direction disparity, one can deduce properties of
repair enzymes, such as the ability (1) to excise preferentially the purine
from one mispair and the pyrimidine from the other for two different R/Y
mispairs from a single heterozygous site and (2) to excise one base
preferentially from unlike R/R or Y/Y mispairs. Frame-shifts usually show
strong disparity in conversion direction, with preferential cutting of the
nonlooped or the looped-out strand of the nonpair in heterozygous h-DNA.
The opposite directions of disparity for frame-shifts and their intragenic
suppressors as Ascobolus suggest that repair enzymes have a strong,
systematic bias as to which strand is cut. The conversion spectra of
mutations induced with different mutagens suggest that the nonlooped strand
is preferentially cut, so that base additions generally convert to mutant
and deletions generally convert to wild-type forms. Especially in
nonfunctional or noncoding DNA, this could cause a general increase in DNA
amounts. Conversion disparity, selection, mutation, and other processes
interact, affecting rates of change in base ratios and total DNA.
相似文献
7.
The ability of vacuoles prepared from V. faba leaves to convert 1-aminocyclopropane-1-carboxylic acid to C2H4 was destroyed when vacuoles were lysed by passage through a hypodermic needle, freezing and thawing, osmotic shock, treatment with ethanol or with a detergent. Ethylene synthesis in the vacuolar fraction was also inhibited by the uncouplers carbonyl cyanide m-chlorophenyl hydrazone and dinitrophenol and by the ionophores valinomycin, nigericin, and A23187. Ethylene formation increased with increasing pH of the incubation medium over the pH range of 5.0–7.5. These observations support the hypothesis that C2H4 biosynthesis in vacuolar preparations is dependent on membrane integrity, possibly because of the requirement for a transmembrane ion gradient.Abbreviations ACC
1-aminocyclopropane-1-carboxylic acid
- AVG
aminoethoxyvinylglycine
- CCCP
carbonyl cyanide m-chlorophenyl hydrazone 相似文献
8.
9.
10.
The rate of exchange of peptide group NH hydrogens with the hydrogens of aqueous solvent is sensitive to neighboring side chains. To evaluate the effects of protein side chains, all 20 naturally occurring amino acids were studied using dipeptide models. Both inductive and steric blocking effects are apparent. The additivity of nearest-neighbor blocking and inductive effects was tested in oligo-and polypeptides and, suprisingly, confirmed. Reference rates for alanine-containing peptides were determined and effects of temperature considered. These results provide the information necessary to evaluate measured protein NH to ND exchange rates by comparing them with rates to be expected for the same amino acid sequence is unstructured aligo- and polypeptides. The application of this approach to protein studies is discussed. © 1993 Wiley-Liss, Inc. 相似文献