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Intraspecific nuclear DNA variation in Drosophila 总被引:18,自引:6,他引:12
We have summarized and analyzed all available nuclear DNA sequence
polymorphism studies for three species of Drosophila, D. melanogaster (24
loci), D. simulans (12 loci), and D. pseudoobscura (5 loci). Our major
findings are: (1) The average nucleotide heterozygosity ranges from about
0.4% to 2% depending upon species and function of the region, i.e., coding
or noncoding. (2) Compared to D. simulans and D. pseudoobscura (which are
about equally variable), D. melanogaster displays a low degree of DNA
polymorphism. (3) Noncoding introns and 3' and 5' flanking DNA shows less
polymorphism than silent sites within coding DNA. (4) X-linked genes are
less variable than autosomal genes. (5) Transition (Ts) and transversion
(Tv) polymorphisms are about equally frequent in non-coding DNA and at
fourfold degenerate sites in coding DNA while Ts polymorphisms outnumber Tv
polymorphisms by about 2:1 in total coding DNA. The increased Ts
polymorphism in coding regions is likely due to the structure of the
genetic code: silent changes are more often Ts's than are replacement
substitutions. (6) The proportion of replacement polymorphisms is
significantly higher in D. melanogaster than in D. simulans. (7) The level
of variation in coding DNA and the adjacent noncoding DNA is significantly
correlated indicating regional effects, most notably recombination. (8)
Surprisingly, the level of polymorphism at silent coding sites in D.
melanogaster is positively correlated with degree of codon usage bias. (9)
Three proposed tests of the neutral theory of DNA polymorphisms have been
performed on the data: Tajima's test, the HKA test, and the
McDonald-Kreitman test. About half of the loci fail to conform to the
expectations of neutral theory by one of the tests. We conclude that many
variables are affecting levels of DNA polymorphism in Drosophila, from
properties of nucleotides to population history and, perhaps, mating
structure. No simple, all encompassing explanation satisfactorily accounts
for the data.
相似文献
24.
Caccone A; Moriyama EN; Gleason JM; Nigro L; Powell JR 《Molecular biology and evolution》1996,13(9):1224-1232
Drosophila melanogaster belongs to a closely related group of eight species
collectively known as the melanogaster subgroup; all are native to
sub-Saharan Africa and islands off the east coast of Africa. The
phylogenetic relationships of most species in this subgroup have been well
documented; however, the three most closely related species, D. simulans,
D. sechellia, and D. mauritiana, have remained problematic from a
phylogenetic standpoint as no data set has unambiguously resolved them. We
present new DNA sequence data on the nullo and Serendipity-alpha genes and
combine them with all available nuclear DNA sequence data; the total data
encompass 12 genes and the ITS of rDNA. A methodological problem arose
because nine of the genes had information on intraspecific polymorphisms in
at least one species. We explored the effect of inclusion/exclusion of
polymorphic sites and found that it had very little effect on phylogenetic
inferences, due largely to the fact that 82% of polymorphisms are
autapomorphies (unique to one species). We have also reanalyzed our
previous DNA-DNA hybridization data with a bootstrap procedure. The
combined sequence data set and the DNA-DNA hybridization data strongly
support the sister status of the two island species, D. sechellia and D.
mauritiana. This at least partially resolves what had been a paradox of
parallel evolution in these two species.
相似文献
25.
Yamini P. Ginotra Shefali N. Ramteke Gulshan R. Walke Srikanth Rapole 《Free radical research》2016,50(4):405-413
The binding of metal ions to Aβ peptide plays an important role in the etiology of AD. Copper coordinates chiefly to His residues and produces reactive oxygen species (ROS) upon redox cycling. ROS builds enormous burden on the normal functioning of neuronal cells and results into deleterious effects. Recently, two structurally distinct copper binding sites with contrasting redox properties were characterized. Here, we demonstrate for the first time the effect of binding of two equivalents of Cu2+ on redox properties and cytotoxicity of Aβ peptide. Our electrochemical data and ascorbate consumption assay suggest that in the presence of two equivalents of copper; Aβ peptide has higher propensity of H2O2 generation. The oxidation of Aβ1–16 peptide due to both gamma radiolysis and metal catalyzed oxidation in the presence of two equivalents of copper is inhibited confirming the binding of both equivalents of copper to peptide. The electrochemical and cytotoxicity study shows that negative shift in the reduction potential is reflected as slightly higher cytotoxicity in SH-SY5Y cell lines for Aβ1–16–Cu2+ (1:2) complex. 相似文献
26.
Brain spectrin, through its beta subunit, binds with high affinity to protein-binding sites on brain membranes quantitatively depleted of ankyrin (Steiner, J., and Bennett, V. (1988) J. Biol. Chem. 263, 14417-14425). In this study, calmodulin is demonstrated to inhibit binding of brain spectrin to synaptosomal membranes. Submicromolar concentrations of calcium are required for inhibition of binding, with half-maximal effects at pCa = 6.5. Calmodulin competitively inhibits binding of spectrin to protein(s) in stripped synaptosomal membranes, with Ki = 1.3 microM in the presence of 10 microM calcium. A reversible receptor-mediated process, and not proteolysis, is responsible for inhibition since the effect of calcium/calmodulin is reversed by the calmodulin antagonist trifluoperazine and by chelation of calcium with sodium [ethylenebis(oxyethylenenitrilo)]tetraacetic acid. The target of calmodulin is most likely the spectrin attachment protein(s) rather than spectrin itself since: (a) membrane binding of the brain spectrin beta subunit, which does not associate with calmodulin, is inhibited by calcium/calmodulin, and (b) red cell spectrin which binds calmodulin very weakly, is inhibited from interacting with membrane receptors in the presence of calcium/calmodulin. Ca2+/calmodulin inhibited association of erythrocyte spectrin with synaptosomal membranes but had no effect on binding of erythrocyte or brain spectrin to ankyrin in erythrocyte membranes. These experiments demonstrate the potential for differential regulation of spectrin-membrane protein interactions, with the consequence that Ca2+/calmodulin can dissociate direct spectrin-membrane interactions locally or regionally without disassembly of the areas of the membrane skeleton stabilized by linkage of spectrin to ankyrin. A membrane protein of Mr = 88,000 has been identified that is dissociated from spectrin affinity columns by calcium/calmodulin and is a candidate for the calmodulin-sensitive spectrin-binding site in brain. 相似文献
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Yaqin Xu Christine Tertilt Anja Krause Luis EN Quadri Ronald G Crystal Stefan Worgall 《Respiratory research》2009,10(1):26
Background
Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Infections of the respiratory tract are a hallmark in CF. The host immune responses in CF are not adequate to eradicate pathogens, such as P. aeruginosa. Dendritic cells (DC) are crucial in initiation and regulation of immune responses. Changes in DC function could contribute to abnormal immune responses on multiple levels. The role of DC in CF lung disease remains unknown.Methods
This study investigated the expression of CFTR gene in bone marrow-derived DC. We compared the differentiation and maturation profile of DC from CF and wild type (WT) mice. We analyzed the gene expression levels in DC from naive CF and WT mice or following P. aeruginosa infection.Results
CFTR is expressed in DC with lower level compared to lung tissue. DC from CF mice showed a delayed in the early phase of differentiation. Gene expression analysis in DC generated from naive CF and WT mice revealed decreased expression of Caveolin-1 (Cav1), a membrane lipid raft protein, in the CF DC compared to WT DC. Consistently, protein and activity levels of the sterol regulatory element binding protein (SREBP), a negative regulator of Cav1 expression, were increased in CF DC. Following exposure to P. aeruginosa, expression of 3β-hydroxysterol-Δ7 reductase (Dhcr7) and stearoyl-CoA desaturase 2 (Scd2), two enzymes involved in the lipid metabolism that are also regulated by SREBP, was less decreased in the CF DC compared to WT DC.Conclusion
These results suggest that CFTR dysfunction in DC affects factors involved in membrane structure and lipid-metabolism, which may contribute to the abnormal inflammatory and immune response characteristic of CF. 相似文献29.
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Crystal structures of two Sm protein complexes and their implications for the assembly of the spliceosomal snRNPs 总被引:19,自引:0,他引:19
Kambach C Walke S Young R Avis JM de la Fortelle E Raker VA Lührmann R Li J Nagai K 《Cell》1999,96(3):375-387
The U1, U2, U4/U6, and U5 small nuclear ribonucleoprotein particles (snRNPs) involved in pre-mRNA splicing contain seven Sm proteins (B/B', D1, D2, D3, E, F, and G) in common, which assemble around the Sm site present in four of the major spliceosomal small nuclear RNAs (snRNAs). These proteins share a common sequence motif in two segments, Sm1 and Sm2, separated by a short variable linker. Crystal structures of two Sm protein complexes, D3B and D1D2, show that these proteins have a common fold containing an N-terminal helix followed by a strongly bent five-stranded antiparallel beta sheet, and the D1D2 and D3B dimers superpose closely in their core regions, including the dimer interfaces. The crystal structures suggest that the seven Sm proteins could form a closed ring and the snRNAs may be bound in the positively charged central hole. 相似文献