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1.
Michael Klutstein Martin Xaver Ronen Shemesh Drora Zenvirth Franz Klein Giora Simchen 《Molecular genetics and genomics : MGG》2009,282(5):453-462
Synapsis of homologs during meiotic prophase I is associated with a protein complex built along the bivalents—the synaptonemal
complex (SC). Mutations in the SC-component gene ZIP1 diminish SC formation, leading to reduced recombination levels and low spore viability. Here we show that in SK1 strains
heterozygous for a deletion of ZIP1 in certain regions meiotic interference are impaired with no decrease in recombination levels. The extent of synapsis is
over all reduced and NDJ levels of a large endogenous chromosome and of artificial chromosomes (YACs) rise to twice the level
of wild type strains. A substantial proportion of mis-segregating YACs had undergone crossing over. This demonstrates that
different functions of Zip1 display differential sensitivities to changes in expression levels. 相似文献
2.
Zenvirth D Richler C Bardhan A Baudat F Barzilai A Wahrman J Simchen G 《Chromosoma》2003,111(6):369-376
Meiotic recombination in yeast is initiated at DNA double-strand breaks (DSBs), processed into 3′ single-strand overhangs that are active in homology search, repair and formation of recombinant molecules. Are 3′ overhangs recombination intermediaries in mouse germ cells too? To answer this question we developed a novel approach based on the properties of the Klenow enzyme. We carried out two different, successive in situ Klenow enzyme-based reactions on sectioned preparations of testicular tubules. Signals showing 3′ overhangs were observed during wild-type mouse spermatogenesis, but not in Spo11 ?/? males, which lack meiotic DSBs. In Atm ?/? mice, abundant positively stained spermatocytes were present, indicating an accumulation of non-repaired DSBs, suggesting the involvement of ATM in repair of meiotic DSBs. Thus the processing of DSBs into 3′ overhangs is common to meiotic cells in mammals and yeast, and probably in all eukaryotes. 相似文献
3.
Na+ strongly promoted HCO3− transport in Anabaena variabilis. The effect was highly specific to this cation. Kinetic analysis indicated a progressive decrease in the Km (HCO3−) of the transport system with increasing Na+ concentration. Vmax was also affected. We raise the possibility that the transport is a Na+-HCO3− symport; alternatively, that a Na+-H+ antiport (or Na+-OH+ symport) system mediates the efflux of the OH− ions derived from the entering HCO3− ions, and that this antiport can rate-limit HCO3− influx. 相似文献
4.
Energization and activation of inorganic carbon uptake by light in cyanobacteria 总被引:11,自引:3,他引:8 下载免费PDF全文
The requirement of the inorganic carbon (Ci) transport system for light in cyanobacteria was investigated in Anabaena variabilis by the filtering centrifugation technique and in a mutant (E1) isolated from Anacystis nidulans using a gas exchange system. Ci transport capability increased with time of preillumination and decreased following darkening. Full activity could not be obtained by operating either photosystem II (PSII) or photosystem I alone. 3(3,4 Dichlorophenyl)-1,1 dimethylurea strongly inhibited Ci uptake. Very low activity of PSII was sufficient to activate Ci uptake. However, in the presence of dithiothreitol PSII activity was not required. We conclude that light may be required to activate as well as to energize Ci uptake in cyanobacteria. 相似文献
5.
Shoshana Klein Drora Zenvirth Vardit Dror Arnold B. Barton David B. Kaback Giora Simchen 《Chromosoma》1996,105(5):276-284
The preferred positions for meiotic double-strand breakage were mapped on Saccharomyces cerevisiae chromosomes I and VI, and on a number of yeast artificial chromosomes carrying human DNA inserts. Each chromosome had strong
and weak double-strand break (DSB) sites. On average one DSB-prone region was detected by pulsed-field gel electrophoresis
per 25 kb of DNA, but each chromosome had a unique distribution of DSB sites. There were no preferred meiotic DSB sites near
the telomeres. DSB-prone regions were associated with all of the known ”hot spots” for meiotic recombination on chromosomes
I, III and VI.
Received: 19 March 1996; in revised form: 26 July 1996 / Accepted: 18 August 1996 相似文献
6.
Sister chromatid-based DNA repair is mediated by RAD54, not by DMC1 or TID1 总被引:3,自引:0,他引:3 下载免费PDF全文
In the mitotic cell cycle of the yeast Saccharomyces cerevisiae, the sister chromatid is preferred over the homologous chromosome (non-sister chromatid) as a substrate for DNA double-strand break repair. However, no genes have yet been shown to be preferentially involved in sister chromatid-mediated repair. We developed a novel method to identify genes that are required for repair by the sister chromatid, using a haploid strain that can embark on meiosis. We show that the recombinational repair gene RAD54 is required primarily for sister chromatid-based repair, whereas TID1, a yeast RAD54 homologue, and the meiotic gene DMC1, are dispensable for this type of repair. Our observations suggest that the sister chromatid repair pathway, which involves RAD54, and the homologous chromosome repair pathway, which involves DMC1, can substitute for one another under some circumstances. Deletion of RAD54 in S.cerevisiae results in a phenotype similar to that found in mammalian cells, namely impaired DNA repair and reduced recombination during mitotic growth, with no apparent effect on meiosis. The principal role of RAD54 in sister chromatid-based repair may also be shared by mammalian and yeast cells. 相似文献
7.
Antibodies elicited in rabbits by chromatin and by purified histone H2B have been used to study the structure of chromatin by immunoelectron microscopy. Chromatin spread on grids reveals a structure of closely packed spherical particles with an average diameter of 104 Å, arranged either in clusters or in linear arrays of beads, some of which have a supercoil-like arrangement. No DNA strings connecting the beads could be observed. Upon antibody binding, the diameter of the particles increases up to 300 Å. This size is compatible with a model where one layer of gamma globulin molecules 110 Å long encircles a sphere of chromatin 100 Å in diameter. The presence of rabbit gamma globulins on the enlarged beads has been verified by the addition of ferritin-labeled goat anti-rabbit gamma globulins. Anti-chromatin sera which react with nonhistone proteins but not with free histones or DNA react with more than 95% of the beads; this suggests that most of the beads contain nonhistone proteins. Since the number of nonhistone proteins is large, it is improbable that each sphere contains a full complement of these proteins. We therefore suggest that the various chromatin spheres contain different types of nonhistone proteins. About 90% of the chromatin spheres reacted with antibodies to histone H2B, suggesting that most of the chromatin beads contain this type of histone. 相似文献
8.
Kobi J Simpson-Lavy Drora Zenvirth Michael Brandeis 《Cell cycle (Georgetown, Tex.)》2015,14(19):3138-3145
The Anaphase Promoting Complex/Cyclosome (APC/C) ubiquitin ligase activated by its G1 specific adaptor protein Cdh1 is a major regulator of the cell cycle. The APC/CCdh1 mediates degradation of dozens of proteins, however, the kinetics and requirements for their degradation are largely unknown. We demonstrate that overexpression of the constitutive active CDH1m11 mutant that is not inhibited by phosphorylation results in mitotic exit in the absence of the FEAR and MEN pathways, and DNA re-replication in the absence of Cdc7 activity. This mode of mitotic exit also reveals additional requirements for APC/CCdh1 substrate degradation, which for some substrates such as Pds1 or Clb5 is dephosphorylation, but for others such as Cdc5 is phosphorylation. 相似文献
9.
Increased Instability of Human CTG Repeat Tracts on Yeast Artificial Chromosomes during Gametogenesis 下载免费PDF全文
Haim Cohen Dorothy D. Sears Drora Zenvirth Philip Hieter Giora Simchen 《Molecular and cellular biology》1999,19(6):4153-4158
Expansion of trinucleotide repeat tracts has been shown to be associated with numerous human diseases. The mechanism and timing of the expansion events are poorly understood, however. We show that CTG repeats, associated with the human DMPK gene and implanted in two homologous yeast artificial chromosomes (YACs), are very unstable. The instability is 6 to 10 times more pronounced in meiosis than during mitotic division. The influence of meiosis on instability is 4.4 times greater when the second YAC with a repeat tract is not present. Most of the changes we observed in trinucleotide repeat tracts are large contractions of 21 to 50 repeats. The orientation of the insert with the repeats has no effect on the frequency and distribution of the contractions. In our experiments, expansions were found almost exclusively during gametogenesis. Genetic analysis of segregating markers among meiotic progeny excluded unequal crossover as the mechanism for instability. These unique patterns have novel implications for possible mechanisms of repeat instability. 相似文献
10.
Nature of the Inorganic Carbon Species Actively Taken Up by the Cyanobacterium Anabaena variabilis 总被引:26,自引:18,他引:8 下载免费PDF全文
The nature of the inorganic carbon (Ci) species actively taken up by cyanobacteria CO2 or HCO3− has been investigated. The kinetics of CO2 uptake, as well as that of HCO3− uptake, indicated the involvement of a saturable process. The apparent affinity of the uptake mechanism for CO2 was higher than that for HCO3−. Though the calculated Vmax was the same in both cases, the maximum rate of uptake actually observed was higher when HCO3− was supplied. Ci uptake was far more sensitive to the carbonic anhydrase inhibitor ethoxyzolamide when CO2 was the species supplied. Observations of photosynthetic rate as a function of intracellular Ci level (following supply of CO2 or HCO3− for 5 seconds) led to the inference that HCO3− is the species which arrives at the inner membrane surface, regardless of the species supplied. When the two species were supplied simultaneously, mutual inhibition of uptake was observed.
On the basis of these and other results, a model is proposed postulating that a carboic anhydrase-like subunit of the Ci transport apparatus binds CO2 and releases HCO3− at or near a membrane porter. The latter transports HCO3− ions to the cell interior.
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