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1.
Mineralization of tooth dentin (the deposition of hydroxyapatite crystals in and around collagen type I fibers of the extracellular matrix) requires the involvement of several genes, among them the gene coding for the dentin matrix protein 1, DMP1. We determined the exon–intron organization of the cattle DMP1 gene and used this information to amplify by the polymerase chain reaction homologous gene fragments from the genomic DNA of two species of metatherian (marsupial) mammals and one prototherian (monotreme) species. The translated proto- and metatherian protein sequences are highly divergent from the eutherian sequences but retain the general characteristics of the DMP1 (high acidity, serine-richness, multiple glycosylation sites, and the presence of the RGD cell attachment tripeptide). They therefore appear to be functional even though, evolutionarily, teeth are in a regression phase in prototherians. It is possible, therefore, that DMP1 is also involved in other functions besides dentinogenesis. The DMP1 gene appears to evolve rapidly and apparently tolerates non-frame-shifting insertions/deletions throughout the coding sequence. Received: 22 February 1998 / Accepted: 11 July 1998 相似文献
2.
Andropin, which encodes an antibacterial protein, is closely linked to the Cecropin gene cluster of D. melanogaster. Andropin and Cecropins are considered to have originated from one common ancestor. However, the expression pattern of Andropin is distinct from that of Cecropins, being restricted to the adult male ejaculatory duct. To elucidate the evolutionary process of Andropin, we have sequenced Andropin genes from D. melanogaster and its closely related species. In D. melanogaster, the nucleotide diversity of Andropin is remarkably low compared to that of Cecropin. In contrast, nonsynonymous substitutions of Andropin are conspicuously frequent between species. From genomic Southern analysis, Andropin-like genes are present in at least the
melanogaster species subgroup. The series of present results suggests that Andropin was born in the course of constructing the Drosophila Cecropin gene family and then started to evolve rapidly, in contrast to Cecropins.
Received: 10 August 2001 / Accepted: 29 October 2001 相似文献
3.
Functional Expression of the Murine Connexin 36 Gene Coding for a Neuron-Specific Gap Junctional Protein 总被引:5,自引:0,他引:5
Teubner B Degen J Söhl G Güldenagel M Bukauskas FF Trexler EB Verselis VK De Zeeuw CI Lee CG Kozak CA Petrasch-Parwez E Dermietzel R Willecke K 《The Journal of membrane biology》2000,176(3):249-262
4.
Cecropin is a type of antibacterial peptide that is synthesized in response to infection and has been characterized in many insect species and one mammal. The Cecropin locus of Drosophila melanogaster also contains the gene Andropin, which has been identified only in this species and encodes a male-specific antibacterial peptide. As a first step in studying the molecular evolution of the cecropin and andropin genes among Drosophila species, we have isolated genomic clones that cover the Cecropin locus in Drosophila virilis. The cloned region totals approximately 25 kb, within which a 9-kb fragment contains four cecropin genes and one pseudogene. All four genes have a high level of sequence homology to D. melanogaster Cecropin, about 80% identity in the coding regions, and the intron positions are conserved. As in D. melanogaster and other insects, κB-related cis-regulatory elements are found upstream of these cecropin genes. An Andropin-related sequence was not identified in D. virilis; however, genome Southern hybridizations suggest that Andropin-related sequences are present in at least the melanogaster species subgroup. Analysis of 19 insect cecropin genes identifies a common ancestral Cecropin before the divergence of Diptera and Lepidoptera. In addition, D. melanogaster and D. virilis can be identified by monophyletic clades for Cecropin. In contrast, the Lepidopteran species show polyphyletic relationships for duplicated cecropin genes. Received: 12 August 1996 / Accepted: 18 October 1996 相似文献
5.
Joachim Schütze Alexander Skorokhod Isabel M. Müller Werner E.G. Müller 《Journal of molecular evolution》2001,53(4-5):402-415
One crucial event during evolution to multicellularity was the development of either direct cell–cell contact or indirect
interaction via extracellular matrix (ECM) molecules. The identification of those polypeptides provides conclusive data on
the phylogenetic relationship of metazoan phyla and helps us to understand the position of the Metazoa among the other kingdoms.
Recently it became evident that the ECM of sponges is amazingly complex; it is composed of fibrous molecules, e.g., collagen,
and their corresponding receptors, which are highly similar to those existing in other metazoan phyla. While these data already
support the view of monophyly of Metazoa, additional studies are required to understand whether these molecules, which are
similar in their primary sequence, also have the same function throughout the metazoan kingdom. In the present study we identified
the ligand for one of the autopomorphic characters of Metazoa, the single-transmembrane receptor protein with the receptor
tyrosine kinase (RTK) from G. cydonium, as an example: the putative mucus-like protein from G. cydonium. This protein was upregulated during autograft fusion in the homologous system with kinetics similar to those of the RTK.
Additionally, a cDNA was isolated from S. domuncula whose deduced polypeptide displays a high sequence similarity to dermatopontin, an ECM molecule found exclusively in Metazoa.
Furthermore, it is documented that expression of the fibrous ECM molecule collagen is regulated by the characteristic metazoan
morphogens myotrophin and endothelial monocyte-activating polypeptide. These data indicate that the ECM of sponges is not
an unstructured ground substance but provides the basis for integrated cell communication.
Received: 26 October 2000 / Accepted: 1 February 2001 相似文献
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Select de novo Gene and Protein Expression During Renal Epithelial Cell Culture in Rotating Wall Vessels is Shear Stress Dependent 总被引:4,自引:0,他引:4
Kaysen JH Campbell WC Majewski RR Goda FO Navar GL Lewis FC Goodwin TJ Hammond TG 《The Journal of membrane biology》1999,168(1):77-89
The rotating wall vessel has gained popularity as a clinical cell culture tool to produce hormonal implants. It is desirable
to understand the mechanisms by which the rotating wall vessel induces genetic changes, if we are to prolong the useful life
of implants. During rotating wall vessel culture gravity is balanced by equal and opposite hydrodynamic forces including shear
stress. The current study provides the first evidence that shear stress response elements, which modulate gene expression
in endothelial cells, are also active in epithelial cells. Rotating wall culture of renal cells changes expression of select
gene products including the giant glycoprotein scavenger receptors cubulin and megalin, the structural microvillar protein
villin, and classic shear stress response genes ICAM, VCAM and MnSOD. Using a putative endothelial cell shear stress response
element binding site as a decoy, we demonstrate the role of this sequence in the regulation of selected genes in epithelial
cells. However, many of the changes observed in the rotating wall vessel are independent of this response element. It remains
to define other genetic response elements modulated during rotating wall vessel culture, including the role of hemodynamics
characterized by 3-dimensionality, low shear and turbulence, and cospatial relation of dissimilar cell types.
Received: 30 June 1998/Revised: 30 November 1998 相似文献
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Whereas the genomes of many organisms contain several nonallelic types of linker histone genes, one single histone H1 type
is known in Drosophila melanogaster that occurs in about 100 copies per genome. Amplification of H1 gene sequences from genomic DNA of wild type strains of D. melanogaster from Oregon, Australia, and central Africa yielded numerous clones that all exhibited restriction patterns identical to each
other and to those of the known H1 gene sequence. Nucleotide sequences encoding the evolutionarily variable domains of H1
were determined in two gene copies of strain Niamey from central Africa and were found to be identical to the known H1 sequence.
Most likely therefore, the translated sequences of D. melanogaster H1 genes do not exhibit intragenomic or intergenomic variations.
In contrast, three different histone H1 genes were isolated from D. virilis and found to encode proteins that differ remarkably from each other and from the H1 of D. melanogaster and D. hydei. About 40 copies of H1 genes are organized in the D. virilis genome with copies of core histone genes in gene quintets that were found to be located in band 25F of chromosome 2. Another
type of histone gene cluster is present in about 15 copies per genome and contains a variable intergenic sequence instead
of an H1 gene. The H1 heterogeneity in D. virilis may have arisen from higher recombination rates than occur near the H1 locus in D. melanogaster and might provide a basis for formation of different chromatin subtypes.
Received: 2 March 2000 / Accepted: 1 June 2000 相似文献
13.
Detailed nucleotide diversity studies revealed that the fil1 gene of Antirrhinum, which has been reported to be single copy, is a member of a gene family composed of at least five genes. In four Antirrhinum majus populations with different mating systems and one A. graniticum population, diversity within populations is very low. Divergence among Antirrhinum species and between Antirrhinum and Digitalis is also low. For three of these genes we also obtained sequences from a more divergent member of the Scrophulariaceae, Verbascum nigrum. Compared with Antirrhinum, little divergence is again observed. These results, together with similar data obtained previously for five cycloidea genes,
suggest either that these gene families (or the Antirrhinum genome) are unusually constrained or that there is a low rate of substitution in these lineages. Using a sample of 52 genes,
based on two measures of codon usage (ENC and GC3 content), we show that cyc and fil1 are among the least biased Antirrhinum genes, so that their low diversity is not due to extreme codon bias.
Received: 20 June 2000 / Accepted: 25 October 2000 相似文献
14.
We examined the ability of SV40-immortalized human and rabbit corneal epithelial cells (HCEC and RCEC, respectively) to adapt
to chronic hypertonic stress. Under isotonic conditions, in the presence of 50 μm bumetanide, proliferation measured as 3H-thymidine incorporation declined in RCEC and HCEC by 8 and 35%, respectively. After 48 hr exposure to 375 mOsm medium, RCEC
proliferation fell by 19% whereas in HCEC it declined by 45%. Light scattering behavior demonstrated that both cell lines
mediate nearly complete regulatory volume increase (RVI) responses to an acute hypertonic (375 mOsm) challenge, which in part
depend on bumetanide-sensitive Na-K-2Cl cotransporter (NKCC) activity. Following exposing RCEC for 48 hr to 375 mOsm medium,
their RVI response to an acute hypertonic challenge was inhibited by 17%. However, in HCEC this response declined by 68%.
During exposure to 375 mOsm medium for up to 24 hr, only RCEC upregulated NKCC gene and protein expression as well as bumetanide-sensitive
86Rb influx. These increases are consistent with the smaller declines in RVI and proliferation capacity occurring during this
period in RCEC than in HCEC. Therefore, adaptation by RCEC to chronic hypertonic stress is dependent on stimulation of NKCC
gene and protein expression and functional activity. On the other hand, under isotonic conditions, HCEC RVI and proliferation
are more dependent on NKCC activity than they are in RCEC.
Received: 7 March 2000/Revised: 18 May 2000 相似文献
15.
Benoit Cousineau Fabrice Leclerc Robert Cedergren 《Journal of molecular evolution》1997,45(6):661-670
Sequence similarity has given rise to the proposal that IF-2, EF-G, and EF-Tu are related through a common ancestor. We evaluate
this proposition and whether the relationship can be extended to other factors of protein synthesis. Analysis of amino acid
sequence similarity gives statistical support for an evolutionary affiliation among IF-1, IF-2, IF-3, EF-Tu, EF-Ts, and EF-G
and suggests further that this association is a result of gene duplication/fusion events. In support of this mechanism, the
three-dimensional structures of IF-3, EF-Tu, and EF-G display a predictable domain structure and overall conformational similarity.
The model that we propose consists of three consecutives duplication/fusion events which would have taken place before the
divergence of the three superkingdoms: eubacteria, archaea, and eukaryotes. The root of this protein superfamily tree would
be an ancestor of the modern IF-1 gene sequence. The repeated fundamental motif of this protein superfamily is a small RNA
binding domain composed of two α-helices packed along side of an antiparallel β-sheet.
Received: 17 October 1996 / Accepted: 10 June 1997 相似文献
16.
Bacteriophage T7 was challenged with either of two toxic genes expressed from plasmids. Each plasmid contained a different
gene downstream of a T7 promoter; cells harboring each plasmid caused an infection by wild-type T7 to abort. T7 evolved resistance
to both inhibitors by avoidance of the plasmid expression system rather than by blocking or bypassing the effects of the specific
toxic gene product. Resistance was due to a combination of mutations in the T7 RNA polymerase and other genes expressed at
the same time as the polymerase. Mutations mapped to sites that are unlikely to alter polymerase specificity for its cognate
promoter but the basis for discrimination between phage and plasmid promoters in vivo was not resolved. A reporter assay indicated that, relative to wild-type phage, gene expression from the plasmid was diminished
several-fold in cells infected by the evolved phages. A recombinant phage, derived from the original mutant but lacking a
mutation in the gene for RNA polymerase, exhibited intermediate activity in the reporter assay and intermediate resistance
to the toxic gene cassettes. Alterations in both RNA polymerase and a second gene are thus responsible for resistance. These
findings have broad evolutionary parallels to other systems in which viral inhibition is activated by viral regulatory signals
such as defective-interfering particles, and they may have mechanistic parallels to the general phenomena of position effects
and gene silencing.
Received: 18 July 2000 / Accepted: 8 February 2001 相似文献
17.
T.E. DeCoursey S.Y. Kim M.R. Silver F.N. Quandt 《The Journal of membrane biology》1996,152(2):141-157
Ion channel expression was studied in THP-1 human monocytic leukemia cells induced to differentiate into macrophage-like cells
by exposure to the phorbol ester, phorbol 12-myristate 13-acetate (PMA). Inactivating delayed rectifier K+ currents, I
DR, present in almost all undifferentiated THP-1 monocytes, were absent from PMA-differentiated macrophages. Two K+ channels were observed in THP-1 cells only after differentiation into macrophages, an inwardly rectifying K+ channel (I
IR) and a Ca2+-activated maxi-K channel (I
BK). I
IR was a classical inward rectifier, conducting large inward currents negative to E
K and very small outward currents. I
IR was blocked in a voltage-dependent manner by Cs+, Na+, and Ba2+, block increasing with hyperpolarization. Block by Na+ and Ba2+ was time-dependent, whereas Cs+ block was too fast to resolve. Rb+ was sparingly permeant. In cell-attached patches with high [K+] in the pipette, the single I
IR channel conductance was ∼30 pS and no outward current could be detected. I
BK channels were observed in cell-attached or inside-out patches and in whole-cell configuration. In cell-attached patches the
conductance was ∼200–250 pS and at potentials positive to ∼100 mV a negative slope conductance of the unitary current was
observed, suggesting block by intracellular Na+. I
BK was activated at large positive potentials in cell-attached patches; in inside-out patches the voltage-activation relationship
was shifted to more negative potentials by increased [Ca2+]. Macroscopic I
BK was blocked by external TEA+ with half block at 0.35 mm. THP-1 cells were found to contain mRNA for Kv1.3 and IRK1. Levels of mRNA coding for these K+ channels were studied by competitive PCR (polymerase chain reaction), and were found to change upon differentiation in the
same direction as did channel expression: IRK1 mRNA increased at least 5-fold, and Kv1.3 mRNA decreased on average 7-fold.
Possible functional correlates of the changes in ion channel expression during differentiation of THP-1 cells are discussed.
Received: 19 September 1995/Revised: 14 March 1996 相似文献
18.
To determine whether the persistent nature of hepatitis C infection is related to the emergence of antigenic variants driven
by immune selection, we examined the sequence heterogeneity in a portion of the hepatitis C virus (HCV) nonstructural 3 (NS3)
gene of a patient infected over the course of more than 2 years. By PCR amplification, cloning, and sequencing, we observed
several variable and conserved regions in the NS3 segment of the HCV genome. All variable regions had higher ratios of nonsynonymous/synonymous
mutations and encompassed immunodominant epitopes, and their locations were not essential to maintain the known function of
HCV RNA helicase. In contrast, the regions that are critical for HCV RNA helicase activity were found to be conserved with
lower heterogeneity or lower ratios of nonsynonymous/synonymous mutations, and none except one of these regions was encoded
within immunodominant epitopes. Our results are consistent with immune selection of viral variants at the epitope and molecular
levels that may enable HCV to evade host defenses over time. Plotting the relatedness of sequence variants revealed a star
topology suggesting that a wild-type HCV sequence is maintained, unlike HIV.
Received: 2 November 2000 / Accepted: 1 October 2001 相似文献
19.
The Drosophila fat body protein 2 gene (Fbp2) is an ancient duplication of the alcohol dehydrogenase gene (Adh) which encodes a protein that differs substantially from ADH in its methionine content. In D. melanogaster, there is one methionine in ADH, while there are 51 (20% of all amino acids) in FBP2. Methionine is involved in 46% of amino
acid replacements when Fbp2 DNA sequences are compared between D. melanogaster and D. pseudoobscura. Methionine accumulation does not affect conserved residues of the ADH-ADHr-FBP2 multigene family. The multigene family has evolved by replacement of mildly hydrophobic amino acids by methionine with
no apparent reversion. Its short-term evolution was compared between two Drosophila species, while its long-term evolution was compared between two genera belonging respectively to acalyptrate and calyptrate
Diptera, Drosophila and Sarcophaga. The pattern of nucleotide substitution was consistent with an independent accumulation of methionines at the Fbp2 locus in each lineage. Under a steady-state model, the rate of methionine accumulation was constant in the lineage leading
to Drosophila, and was twice as fast as that in the calyptrate lineage. Substitution rates were consistent with a slight positive selective
advantage for each methionine change in about one-half of amino acid sites in Drosophila. This shows that selection can potentially account for a large proportion of amino acid replacements in the molecular evolution
of proteins.
Received: 12 December 1994 / Accepted: 15 April 1996 相似文献