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41.
Mutations which improve the efficiency of recombination should affect
either the proteins which mediate recombination or their substrate, DNA
itself. The former mutations would be localized to a few sites. The latter
would be dispersed. Studies of hybridization between RNA molecules have
suggested that recombination may be initiated by a homology search
involving the "kissing" of the tips of stem loops. This predicts that, in
the absence of other constraints, mutations which assist the formation of
stem loops would be favored. From comparisons of the folding of normal and
shuffled DNA sequences, I present evidence for an evolutionary selection
pressure to distribute stem loops generally throughout genomes. I propose
that this early pressure came into conflict with later local pressures to
impose information concerning specific function. The conflict was
accommodated by permitting sections of DNA concerned with a specific
function to evolve in dispersed segments. Traces of the conflict seem to be
present in some modern intron-containing genes. Thus, introns may have
allowed the interspersing of selectively advantageous stem loops in coding
regions of DNA.
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A requirement for trypsin-sensitive cell-surface components for cell-cell interactions of embryonic neural retina cells 总被引:5,自引:3,他引:2 下载免费PDF全文
A quantitative assay was used to measure the rate of collection of a population of embryonic neural retina cells to the surface of cell aggregates. The rate of collection of freshly trysinized cells was limited in the initial stages by the rate of replacement of trypsin-sensitive cell- surface components. When cells were preincubated, or "recovered," and then added to cell aggregates, collection occurred at a linear rate and was independent of protein and glycoprotein synthesis. The adhesion of recovered cells was temperature and energy dependent, and was reversibly inhibited by cytochalasin B. Colchicine had little effect on collection of recovered cells. Antiserum directed against recovered cell membranes was shown to bind to recovered cells by indirect immunofluorescence. The antiserum also was shown to inhibit collection of recovered cells to aggregates, suggesting that at least some of the antigens identified might be involved in the adhesion process. The inhibitory effect of the antiserum was dose dependent . Freshly trypsinized cells absorbed neither the immunofluorescence activity nor the adhesion-inhibiting activity. Recovered cells absorbed away both activities. In specificity studies, dorsal neural retina cells adhered to aggregates of ventral optic tectum in preference to aggregates of dorsal optic tectum. The adhesive specificity of the dorsal retina cells was less sensitive to trypsin than the adhesive specificity of ventral retina cells which adhered preferentially to dorsal tectal aggregates only after a period of recovery. 相似文献
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Hasmik Keshishian E Robert McDonald III Filip Mundt Randy Melanson Karsten Krug Dale A Porter Luke Wallace Dominique Forestier Bokang Rabasha Sara E Marlow Judit JaneValbuena Ellen Todres Harrison Specht Margaret Lea Robinson Pierre M Jean Beltran Ozgun Babur Meagan E Olive Javad Golji Eric Kuhn Michael Burgess Melanie A MacMullan Tomas Rejtar Karen Wang DR Mani Shankha Satpathy Michael A Gillette William R Sellers Steven A Carr 《Molecular systems biology》2021,17(9)
Reliable methods to quantify dynamic signaling changes across diverse pathways are needed to better understand the effects of disease and drug treatment in cells and tissues but are presently lacking. Here, we present SigPath, a targeted mass spectrometry (MS) assay that measures 284 phosphosites in 200 phosphoproteins of biological interest. SigPath probes a broad swath of signaling biology with high throughput and quantitative precision. We applied the assay to investigate changes in phospho‐signaling in drug‐treated cancer cell lines, breast cancer preclinical models, and human medulloblastoma tumors. In addition to validating previous findings, SigPath detected and quantified a large number of differentially regulated phosphosites newly associated with disease models and human tumors at baseline or with drug perturbation. Our results highlight the potential of SigPath to monitor phosphoproteomic signaling events and to nominate mechanistic hypotheses regarding oncogenesis, response, and resistance to therapy. 相似文献
45.
Russell L Legg Jessica R Tolman Cameron T Lovinger Edwin D Lephart Kenneth DR Setchell Merrill J Christensen 《Reproductive biology and endocrinology : RB&E》2008,6(1):57
Background
High dietary intake of selenium or soybean isoflavones reduces prostate cancer risk. These components each affect androgen-regulated gene expression. The objective of this work was to determine the combined effects of selenium and isoflavones on androgen-regulated gene expression in rat prostate. 相似文献46.
Lihong?BuEmail author Kenneth?DR?Setchell Edwin?D?Lephart 《Reproductive biology and endocrinology : RB&E》2005,3(1):58
Background
Isoflavones, the most abundant phytoestrogens in soy foods, are structurally similar to 17beta-estradiol. Few studies have examined the nociception and stress hormone responses after consumption of soy isoflavones. 相似文献47.
Thirty-four cytochrome P-450 sequences from one bacterial and six
vertebrate species have been aligned with the aid of a computer alignment
algorithm. Phylogenetic trees were constructed using the
unweighted-pair-group and neighbor-joining methods. The two trees differed
at only a single branch point near the base of the tree. The cytochrome
P-450 superfamily of proteins clustered into eight families and contained
16 gene-duplication events. The first gene duplication occurred
approximately 1,360 Myr before the present (Mybp) and gave rise to
cytochrome P-450s found in two different cellular organelles, the
mitochondria and the endoplasmic reticulum. Both groups utilize cholesterol
or its metabolites as substrates, implying that cholesterol existed greater
than 1,360 Mybp. The fourth gene duplication (approximately 900 Mybp) gave
rise to the drug-metabolizing P-450s. These proteins aid in the
detoxification of foreign chemicals, as opposed to the metabolism of
endogenous compounds. The importance of the capacity to metabolize drugs is
reflected in 11 further gene duplications occurring in this lineage. The
first occurred approximately 800 Mybp and gave rise to the two major P-450
families, the phenobarbital and 3-methylcholanthrene families. An apparent
increase in the rate of cytochrome P-450 evolution is noted between the
bird-mammal divergence (300 Mybp) and the mammalian radiation (75 Mybp).
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