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1.
There is a mosaic pattern of variation between the two tandemly arranged human alpha 1-acid glycoprotein genes. Both the synonymous and the nonsynonymous sites of exons 3 and 4 are more divergent than the rest of the gene, suggesting that they have had a different evolutionary history. Comparisons of the two gene sequences with rat AGP indicate that exons 3 and 4 of AGP2 have been evolving without functional constraint since their divergence from AGP1. It is proposed that the conserved region of the gene has been homogenized recently by gene conversion with the homologous regions of AGP1. The Alu sequences surrounding the genes appear to have been involved in both the gene duplication and the gene conversion events. 相似文献
2.
To study the evolution of human X-linked red and green opsin genes, genomic sequences in large regions of the two genes were
compared. The divergences in introns 3, 4, and 5 and the 3′ flanking sequence of the two genes are significantly lower than
those in exons 4 and 5. The homogenization mechanism of introns and the 3′ flanking sequence of human red and green opsin
genes is probably gene conversion, which also occurred in exons 1 and 6. At least one gene conversion event occurred in each
of three regions (1, 3, and 5) in the sequences compared. In conclusion, gene conversion has occurred frequently between human
red and green opsin genes, but exons 2, 3, 4, and 5 have been maintained distinct between the two genes by natural selection.
Received: 29 September 1997 / Accepted: 29 September 1997 相似文献
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ThelpA1/Gpcr26locus encodes the first cloned and identified G-protein-coupled receptor that specifically interacts with lysophosphatidic acid. A murine full-length cDNA of size consistent with that seen on Northern blots (3.7 kb) was determined using 3′ rapid amplification of cDNA ends. Analysis of genomic clones revealed that the gene is divided into five exons, with one intron inserted in the coding region for transmembrane domain VI and one exon encoding the divergent 5′ sequence in another published cDNA clone variant (orphan receptor mrec1.3). This structure differs from the intronless coding region for a homologous receptor,Edg1,but is identical to another more similar orphan receptor (lpA2) that has been deposited with GenBank. Using backcross analysis, both exons 1 and 4 mapped to a proximal region of murine Chromosome 4 indistinguishable from the vacillans gene. Exon 4 also mapped to a second locus on proximal Chromosome 6 inMus spretus,and this partial duplication was confirmed by Southern blot. The genomic structure indicates a distinct, divergent evolutionary lineage for thevzg-1/lpA1subfamily of receptors compared to those of homologous orphan receptor genes. 相似文献
5.
Gene conversion and natural selection in the evolution of X-linked color vision genes in higher primates 总被引:2,自引:1,他引:1
During higher primate evolution, gene conversion seems to have occurred
often between the red and green photo-pigment genes, which are tandemly
linked on the X chromosome. To understand this phenomenon better, intron 4
sequences of the red and green pigment genes of a male human (an Asian
Indian), a male chimpanzee, and a male baboon were amplified by PCR and
sequenced. The data show that the intron 4 sequences between the two genes
have been strongly or completely homogenized in the three species studied.
Apparently recent gene conversion events have occurred in introns 4 of the
red and green pigment genes in humans and chimpanzees. Two or more
conversion events may have occurred at different times in introns 4 of the
two pigment genes in baboons. The divergence between the two genes is
significantly lower in intron 4 than in exons 4 and 5 in each species,
contrary to the usual situation that introns evolve faster than exons. It
is most likely that strong natural selection for maintaining the distinct
functions of exons 4 and 5 of the red and green pigment genes has acted
against sequence homogenization of these exons.
相似文献
6.
A human immunoglobulinIGHG3 allele (Gmb0, b1, c3, c5, u) with anIGHG4 converted region and three hinge exons 总被引:1,自引:1,他引:0
The five humanIGHG genes consist of three constant domain exons plus one of or four hinge exon(s), the quadruplicated hinge region being characteristic
of theIGHG3 gene. Besides this structural difference, theIGHG genes are polymorphic, as demonstrated by the restriction fragment length polymorphism and, at the protein level, by the
Gm allotypic antigenic determinants. In this paper, we report the sequence of theG3m(b0, b1, c3, c5, u) IGHG3 allele, typical of the Black African populations and of populations with Negroid admixture, found in a homozygous Tunisian
designated as LAT. We demonstrate that thisG3 allele contains only three hinge exons instead of four (the probable result of an unequal crossing over) and thatIGHG3 genes with triplicated hinge exons (and therefore encoding shorter γ 3 chains) are present in healthy individuals from different
populations. Moreover, we show that the LAT G3m (b0, b1, c3, c5, u) coding sequence results from the conversion, in the CH3
exon, of theG3m (b0, b1, b3, b4, b5, u, v) allele, the most frequentIGHG3 gene in the Negroid populations, by the homologous region of aIGHG4 gene. The structural features of theLAT IGHG3 allele, which are the lack of one hinge exon and its conversion by theIGHG4 gene, demonstrate that both crossing-over and gene conversion events occur in the evolution of the humanIGHG genes.
The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have
been assigned the accession number X16110. 相似文献
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Laurie A. Dempsey Ming-jie Li Angela DePace Patricia Bray-Ward Nancy Maizels 《Genomics》1998,49(3):378
The hnRNP D protein interacts with nucleic acids bothin vivoandin vitro.Like many other proteins that interact with RNA, it contains RBD (or “RRM”) domains and arg-gly-gly (RGG) motifs. We have examined the organization and localization of the human and murine genes that encode the hnRNP D protein. Comparison of the predicted sequences of the hnRNP D proteins in human and mouse shows that they are 96.9% identical (98.9% similar). This very high level of conservation suggests a critical function for hnRNP D. Sequence analysis of the humanHNRPDgene shows that the protein is encoded by eight exons and that two additional exons specify sequences in the 3′ UTR. Use of two of the coding exons is determined by alternative splicing of theHNRPDmRNA. The humanHNRPDgene maps to 4q21. The mouseHnrpdgene maps to the F region of chromosome 3, which is syntenic with the human 4q21 region. 相似文献
9.
Hideoki Yokouchi Akira Horii Mitsuru Emi Naohiro Tomita Sadayuki Doi Michio Ogawa Takesada Mori Kenichi Matsubara 《Gene》1990,90(2)
We have previously reported concerning the existence of a third type of human α-amylase gene, AMY3 [Emi et al., Gene 62 (1988) 229–235; Tomita et al., Gene 76 (1989) 11–18], which is expressed in a lung carcinoid tissue, and differs in nucleotide sequence from the two previously characterized human α-amylase genes coding for salivary and pancreatic isozymes, termed AMY1 and AMY2, respectively.Here, we rename this gene AMY2B to coincide with the designation by Gumucio et al. [Mol. Cell Biol. 8 (1988) 1197–1205] and describe its genetic properties as revealed by sequencing studies. It consists of ten major exons whose sequences are highly homologous to those of AMY1 and AMY2. Not only the exons, but also most of the introns seem to be highly conserved, as judged from physical mapping data. The AMY2B gene identified from mRNA in a lung carcinoid tissue has at least two additional untranslated exons in its 5′ region; hence the promoter lies far upstream relative to the other two AMY genes. 相似文献
10.
《Genomics》1995,29(3)
By using primers complementary to the rat βB1 crystallin gene sequence, we amplified exons 5 and 6 of the orthologous human gene (CRYBB1). The amplified human segments displayed greater than 88% sequence homology to the corresponding rat and bovine sequences.CRYBB1was assigned to the group 5 region in 22q11.2–q12.1 by hybridizing the exon 6 PCR product to somatic cell hybrids containing defined portions of human chromosome 22. The exon 5 and exon 6 PCR products ofCRYBB1were used to localize, by interspecific backcross mapping, the mouse gene (Crybb1) to the central portion of chromosome 5. Three other β crystallin genes (βB2(−1), βB3, and βA4) have previously been mapped to the same regions in human and mouse. We demonstrate that the βB1 and βA4 crystallin genes are very closely linked in the two species. These assignments complete the mapping and identification of the human and mouse homologues of the major β crystallins genes that are expressed in the bovine lens. 相似文献
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Gene libraries of the micronucleus and the macronuclear anlagen of the polytene chromosome stage of Stylonychia lemnae were screened for internal C4A4 repeats. The number of these internal repeats was shown to be identical in both kinds of nuclei. Analysis of macronuclear sequences associated with C4A4 in the polytene chromosomes showed that several macronuclear DNA sequences are clustered. However, interspersed between short exons of one gene are located exons of several other genes, i.e. the exon of one gene is an intron for several other genes.by M. Trendelenburg 相似文献
13.
The association of the HLA class III region with many diseases motivates the investigation of unidentified genes in the 30-kb segment between complement component genesBfandC4. RD,which codes for a putative RNA binding protein, is 205 bp downstream ofBf. SKI2W(HGMW-approved symbol SKIV2L), a DEVH-box gene probably involved in RNA turnover, is 171 bp downstream ofRD(HGMW-approved symbol D6S45).RP1(HGMW-approved symbol D6S60E) is located 611 bp upstream ofC4.The DNA sequence between humanRDandRP1was determined and the exon–intron structure ofSKI2Welucidated.SKI2Wconsists of 28 exons. The putative RNA helicase domain of Ski2w is encoded by 9 exons. Further analysis of the 2.5-kb intergenic sequence betweenSKI2WandRP1led to the discovery ofDOM3Z.The full-length cDNA sequence ofDOM3Zencodes 396 amino acids with a leucine zipper motif. Dom3z-related proteins are present in simple and complex eukaryotes. InCaenorhabditis elegans,Dom3z-related protein could be involved in the development of germ cells. HumanRD–SKI2WandDOM3Z–RP1are arranged as two head-to-head oriented gene pairs with unmethylated CpG sequences at the common 5′ regulatory region of each gene pair. The ubiquitous expression pattern suggests that these four genes are probably housekeeping genes. 相似文献
14.
Basement membrane (type IV) collagen, a subfamily of the collagen protein family, is encoded by six distinct genes in mammals. Three of those,COL4A3, COL4A4,andCOL4A5,are linked with Alport syndrome (hereditary nephritis). Patients with leimoyomatosis associated with Alport syndrome have been shown to have deletions in the 5′ end of theCOL4A6gene, in addition to having deletions inCOL4A5(Zhouet al., Science261: 1167–1169, 1993). The humanCOL4A6gene is reported to be 425 kb as determined by mapping of overlapping YAC clones by probes for its 5′ and 3′ ends. In the present study we describe the complete exon/intron size pattern of the humanCOL4A6gene. The 12 λ phage clones characterized in the study spanned a total of 110 kb, including 85 kb of the actual gene and 25 kb of flanking sequences. The overlapping clones contained all 46 exons of the gene and all introns, except for intron 2. Since the total size of the exons and all introns except for intron 2 is about 85 kb, intron 2 must be about 340 kb. All exons of the gene were assigned toEcoRI restriction fragments to facilitate analysis of the gene in patients with leiomyomatosis associated with Alport syndrome. The exon size pattern ofCOL4A6is highly homologous with that of the human and mouseCOL4A2genes, with 27 of the 46 exons ofCOL4A6being identical in size between the genes. 相似文献
15.
Human orosomucoid polymorphism: molecular basis of the three common ORM1 alleles, ORM1*F1, ORM1*F2, and ORM1*S 总被引:3,自引:0,他引:3
I. Yuasa Kazuo Umetsu Ulrike Vogt Hiroaki Nakamura Eiji Nanba Nobuto Tamaki Yoshito Irizawa 《Human genetics》1997,99(3):393-398
The human orosomucoid (ORM) is controlled by two closely linked loci, ORM1 and ORM2, and two tandem genes, AGP1 and AGP2,
encoding the proteins produced by the two loci, have been cloned. In this study the molecular basis of ORM1 polymorphism was
investigated. For the detection of mutations the products of the six exons of each gene, amplified by the polymerase chain
reaction (PCR), were screened by single-strand conformation polymorphism analysis. Subsequently, the exons with an altered
migration pattern were gene-specifically amplified by nested PCR. Sequencing of the gene-specific PCR products showed that
the three common ORM1 alleles result from A→G transitions at the codons for amino acid positions 20 in exon 1 and 156 in exon
5 of the AGP1 gene: ORM1*F1 was characterized by CAG (Gln) and GTG (Val), ORM1*F2, by CAG (Gln) and ATG (Met), and ORM1*S,
by CGG (Arg) and GTG (Val). The phylogenesis of the genes encoding these three ORM1 alleles is discussed.
Received: 5 September 1996 相似文献
16.
植物DUR3同源蛋白属于钠离子/溶质共运蛋白家族的尿素高亲和力运输蛋白,在植物体对外源尿素的主动吸收及内源尿素的再分配过程中具有重要作用。为明确棉花DUR3基因的结构和进化情况,基于生物信息学的方法,从全基因组水平鉴定陆地棉和雷蒙德氏棉的DUR3基因,并对基因结构、跨膜结构域、基序分布、进化关系等进行分析。结果表明:(1)从陆地棉A亚组和D亚组染色体各鉴定出1个DUR3基因,从雷蒙德氏棉基因组鉴定出1个DUR3基因。这3个棉花DUR3同源蛋白同其他植物DUR3同源蛋白一样,具有15个跨膜结构域,具有3个位置一致、高度保守的基序。(2)基因结构分析表明,双子叶植物DUR3基因的外显子个数明显多于单子叶植物,这3个棉花DUR3基因的外显子个数亦是如此。(3)根据物种间种属亲缘关系,对不同物种DUR3氨基酸序列构建的进化树显示,棉花的同双子叶植物的聚在一起。(4)DUR3直系同源基因和旁系同源基因的Ka/Ks比值普遍均大于1,说明这些基因在进化过程中主要受到正向选择的作用。该研究结果为深入研究棉花DUR3同源蛋白提供了理论基础。 相似文献
17.
《FEBS letters》1987,224(2):297-305
Analysis of the structure of the 3′-end of the human α2(IV) gene demonstrated that the α1(IV) and α2(IV) genes have diverged extensively in spite of the apparent homology of the respective gene products. The NC-1 domain and the 3′-untranslated region are encoded by three exons in the α2(IV) gene but five exons in the α1(IV) gene. The two introns present in the NC- 1 domain coding part of the α2(IV) gene had the same location as two of the introns of the α1(IV) gene. The junction exon in the α2(IV) gene contains 53 bp coding for Gly-X-Y sequences whereas there are 71 bp in the α1(IV) gene. Three other Gly-X-Y coding exons studied from the human ⇌2(IV) gene have sizes that differ from corresponding exons in the α1(IV) gene and only one intron location matches here between the two genes. None of the exons studied has 54 bp or multiples thereof. 相似文献
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Christophe Brugidou Isabelle Marty Yvette Chartier Yves Meyer 《Molecular & general genetics : MGG》1993,238(1-2):285-293
A Nicotiana tabacum thioredoxin h gene (EMBL Accession No. Z11803) encoding a new thioredoxin (called h2) was isolated using thioredoxin h1 cDNA (X58527), and represents the first thioredoxin h gene isolated from a higher plant. It encodes a polypeptide of 118 amino acids with the conserved thioredoxin active site Trp-Cys-Gly-Pro-Cys. This gene comprises two introns which have lengths of 1071 and 147 by respectively, and three exons which encode peptides of 29, 41 and 48 amino acids, respectively. This thioredoxin h shows 66% identity with the amino acid sequence of thioredoxin h1 (X58527) and only around 35% with the choroplastic thioredoxins. The two thioredoxins, h1 and h2, do not have any signal peptides and are most probably cytoplasmic. Using the 3 regions of the mRNAs, two probes specific for thioredoxins h1 and h2 have been prepared. Southern blot analysis shows that thioredoxin sequences are present in only two genomic EcoRI fragments: a 3.3 kb fragment encodes h1 and a 4.5 kb fragment encodes h2. Analysis of the ancestors of the allotetraploid N. tabacum shows that thioredoxin h2 is present in N. sylvestris and N. tomentosiformis but that thioredoxin h1 is absent from both putative ancestors. Thus, the thioredoxin h1 gene has probably been recently introduced in to N. tabacum as a gene of agronomic importance, or linked to such genes. Northern blot analysis shows that both genes are expressed in N. tabacum, mostly in organs or tissues that contain growing cells. Thioredoxin h1 is always expressed at a lower level than h2 in tobacco plants. In contrast, the thioredoxin hl gene is abundantly expressed in freshly isolated protoplasts, while h2 mRNAs are not detectable. 相似文献
20.
The extracellular hemoglobins of cladocerans derive from the aggregation of 12 two-domain globin subunits that are apparently
encoded by four genes. This study establishes that at least some of these genes occur as a tandem array in both Daphnia magna and Daphnia exilis. The genes share a uniform structure; a bridge intron separates two globin domains which each include three exons and two
introns. Introns are small, averaging just 77 bp, but a longer sequence (2.2–3.2 kb) separates adjacent globin genes. A survey
of structural diversity in globin genes from other daphniids revealed three independent cases of intron loss, but exon lengths
were identical, excepting a 3-bp insertion in exon 5 of Simocephalus. Heterogeneity in the extent of nucleotide divergence was marked among exons, largely as a result of the pronounced diversification
of the terminal exon. This variation reflected, in part, varying exposure to concerted evolution. Conversion events were frequent
in exons 1–4 but were absent from exons 5 and 6. Because of this difference, the results of phylogenetic analyses were strongly
affected by the sequences employed in this construction. Phylogenies based on total nucleotide divergence in exons 1–4 revealed
affinities among all genes isolated from a single species, reflecting the impact of gene conversion events. In contrast, phylogenies
based on total nucleotide divergence in exons 5 and 6 revealed affinities among orthologous genes from different taxa.
Received: 8 March 1999 / Accepted: 14 July 1999 相似文献