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1.
Satoko Iwahori Daisuke Kohmon Junya Kobayashi Yuhei Tani Takashi Yugawa Kenshi Komatsu 《Cell cycle (Georgetown, Tex.)》2014,13(3):471-481
Ataxia-telangiectasia mutated (ATM) plays crucial roles in DNA damage responses, especially with regard to DNA double-strand breaks (DSBs). However, it appears that ATM can be activated not only by DSB, but also by some changes in chromatin architecture, suggesting potential ATM function in cell cycle control. Here, we found that ATM is involved in timely degradation of Cdt1, a critical replication licensing factor, during the unperturbed S phase. At least in certain cell types, degradation of p27Kip1 was also impaired by ATM inhibition. The novel ATM function for Cdt1 regulation was dependent on its kinase activity and NBS1. Indeed, we found that ATM is moderately phosphorylated at Ser1981 during the S phase. ATM silencing induced partial reduction in levels of Skp2, a component of SCFSkp2 ubiquitin ligase that controls Cdt1 degradation. Furthermore, Skp2 silencing resulted in Cdt1 stabilization like ATM inhibition. In addition, as reported previously, ATM silencing partially prevented Akt phosphorylation at Ser473, indicative of its activation, and Akt inhibition led to modest stabilization of Cdt1. Therefore, the ATM-Akt-SCFSkp2 pathway may partly contribute to the novel ATM function. Finally, ATM inhibition rendered cells hypersensitive to induction of re-replication, indicating importance for maintenance of genome stability. 相似文献
2.
Hyun I. Park 《Analytical biochemistry》2010,396(2):262-60
Matrix metalloproteinases (MMPs) are a family of hydrolytic enzymes that play significant roles in development, morphogenesis, inflammation, and cancer invasion. Endometase (matrilysin 2 or MMP-26) is a putative early biomarker for human carcinomas. The effects of the ionic and nonionic detergents on catalytic activity of endometase were investigated. The hydrolytic activity of endometase was detergent concentration dependent, exhibiting a bell-shaped curve with its maximum activity near the critical micelle concentration (CMC) of nonionic detergents tested. The effect of Brij-35 on human gelatinase B (MMP-9), matrilysin (MMP-7), and membrane-type 1 MMP (MT1-MMP) was further explored. Their maximum catalysis was observed near the CMC of Brij-35 (∼ 90 μM). Their IC50 values were above the CMC. The inhibition mechanism of MMP-7, MMP-9, and MT1-MMP by Brij-35 was a mixed type as determined by Dixon’s plot; however, the inhibition mechanism of endometase was noncompetitive with a Ki value of 240 μM. The catalytic activities of MMPs are influenced by detergents. Monomer of detergents may activate and stabilize MMPs to enhance catalysis, but micelle of detergents may sequester enzyme and block the substrate binding site to impede catalysis. Under physiological conditions, a lipid or membrane microenvironment may regulate enzymatic activity. 相似文献
3.
Sergei L Kosakovsky Pond Sadie R Wisotsky Ananias Escalante Brittany Rife Magalis Steven Weaver 《Molecular biology and evolution》2021,38(3):1184
A number of evolutionary hypotheses can be tested by comparing selective pressures among sets of branches in a phylogenetic tree. When the question of interest is to identify specific sites within genes that may be evolving differently, a common approach is to perform separate analyses on subsets of sequences and compare parameter estimates in a post hoc fashion. This approach is statistically suboptimal and not always applicable. Here, we develop a simple extension of a popular fixed effects likelihood method in the context of codon-based evolutionary phylogenetic maximum likelihood testing, Contrast-FEL. It is suitable for identifying individual alignment sites where any among the sets of branches in a phylogenetic tree have detectably different ω ratios, indicative of different selective regimes. Using extensive simulations, we show that Contrast-FEL delivers good power, exceeding 90% for sufficiently large differences, while maintaining tight control over false positive rates, when the model is correctly specified. We conclude by applying Contrast-FEL to data from five previously published studies spanning a diverse range of organisms and focusing on different evolutionary questions. 相似文献
4.
In Central Europe as in most other temperate regions of the world, Buddleja davidii has become a very successful invader. A thorough observation, documentation and analysis of the spread of invasive species is the precondition for the understanding of invasion processes. Therefore, I documented the occurrence of the species along a west–east transect as well as an altitudinal transect, and I tried to reconstruct the spread of the species in the course of the last decades along railroad areas, which have proved to be the most favorized habitats for colonization of Buddleja. Additionally, a literature review is given on its general spread and distribution in Germany. Based on the investigation of 52 stations, the results show that the species, in Germany, has its optimum in the Rhein-Ruhr- and the Rhein-Main-area, that its abundance significantly decreases from west to east and with increasing altitude. A literature review combined with own investigations shows, that it was very successful in Germany on ruins of World War II but decreased and sometimes totally disappeared in cities of East Germany and of the altitudinal higher regions of Germany, i.e. also in many towns of South Germany. In West Germany, the recent spread started about three decades ago and is still in process. As cold winters seem to be the limiting factor for the spread of Buddleja, even an accelerated spread of this species and perhaps a loss of its ruderal character can be expected, considering the progress of climate change. 相似文献
5.
Aim This study aims to document the floristic changes that occurred in Iceland between 15 and 6 Ma and to establish the dispersal mechanisms for the plant taxa encountered. Using changing patterns of dispersal, two factors controlling floristic changes are tested. Possible factors are (1) climate change, and (2) the changing biogeography of Iceland over the time interval studied; that is, the presence or absence of a Miocene North Atlantic Land Bridge. Location The North Atlantic. Methods Species lists of fossil plants from Iceland in the time period 15 to 6 Ma were compiled using published data and new data. Closest living analogues were used to establish dispersal properties for the fossil taxa. Dispersal mechanisms of fossil plants were then used to reconstruct how Iceland was colonized during various periods. Results Miocene floras of Iceland (15–6 Ma) show relatively high floristic turnover from the oldest floras towards the youngest; and few taxa from the oldest floras persist in the younger floras. The frequencies of the various dispersal mechanisms seen in the 15‐Ma floras are quite different from those recorded in the 6‐Ma floras, and there is a gradual change in the prevailing mode of dispersal from short‐distance anemochory and dyschory to long‐distance anemochory. Two mechanisms can be used to explain changing floral composition: (1) climate change, and (2) the interaction between the dispersal mechanisms of plants and the increasing isolation of proto‐Iceland during the Miocene. Main conclusions Dispersal mechanisms can be used to extract palaeogeographic signals from fossil floras. The composition of floras and dispersal mechanisms indicate that Iceland was connected both to Greenland and to Europe in the early Middle Miocene, allowing transcontinental migration. The change in prevalence of dispersal modes from 15 to 6 Ma appears to reflect the break‐up of a land bridge and the increasing isolation of Iceland after 12 Ma. Concurrent gradual cooling and isolation caused changes in species composition. Specifically, the widening of the North Atlantic Ocean prevented taxa with limited dispersal capability from colonizing Iceland, while climate cooling led to the extinction of thermophilous taxa. 相似文献
6.
Ernst Mayr 《Biology & philosophy》1988,3(4):431-441
The biological species concept deals both with the meaning of the sexual species as a harmonious gene pool and with its protection against deleterious outbreeding (effected by isolating mechanisms). According to the Darwin-Muller-Mayr theory isolating mechanisms are acquired by incipient species during alloparty. Isolating mechanisms are not the result of ad hoc selection, but of a change of function of properties acquired during the preceding isolation of the incipient species. The role of behavioral properties (recognition) among the isolating mechanisms has long been recognized and described by naturalists but was rejected as basis of a species definition for a number of valid reasons. 相似文献
7.
8.
Mechanisms of action of abscisic acid at the cellular level 总被引:11,自引:2,他引:9
9.
Chlorinated methanes are important environmental pollutants, which can be metabolized by bacteria. The biotransformation of chlorinated methanes by bacteria has been shown to be due either to gratuitous metabolism (cometabolism) or their use as a source of carbon and energy. The reactions which result in carbon-halogen bond cleavage include substitutive, reductive, oxygenative, and gem-elimination mechanisms. Certain methylotrophic bacteria can use dichloromethane as a source of carbon and energy. Dichloromethane dehalogenase catalyzes the first substitutive reaction in this metabolism. The enzyme shows a 1010-fold rate enhancement over the reaction of the bisulfide anion with dichloromethane in water. Pseudomonas putida G786 synthesizes cytochrome P-450CAM which catalyzes the gratuitous reduction of chlorinated methanes. These studies with purified enzymes are beginning to reveal more detailed mechanistic features of bacterial chlorinated methane metabolism.Abbreviations DNA
deoxyribonucleic acid
- kcat
catalytic first order rate constant for an enzyme catalyzed reaction
- KM
Michaelis constant for an enzyme catalyzed reaction
- MNDO
modified neglect of diatomic overlap
- PIMA
pattern induced multialignment
- DCMD
dichloromethane dehalogenase 相似文献
10.
David L. Evans 《Entomologia Experimentalis et Applicata》1986,40(3):209-214
It was suggested by Heinrich that cryptic, palatable caterpillars would adopt foliar foraging techniques which would reduce the chance of their being detected. I wished to test this hypothesis further and to determine the post-discovery tactics. I found that caterpillars of Larentia clavaria pallidat, contrary to expectations, usually rested on upper surfaces of young Althaea setosa leaves but moved to the undersides when exposed to higher light intensities. This species may be effectively concealed by older canopy leaves. These larvae usually responded to predator-like stimuli by assuming a deimatic s form but rarely dropped. Dropping may be infrequent partly because younger caterpillars could not easily relocate the foot plant. I discuss, briefly the implications of host-plant selection. 相似文献