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The sequence of the gorilla fetal globin genes: evidence for multiple gene conversions in human evolution 总被引:7,自引:1,他引:7
A F Scott P Heath S Trusko S H Boyer W Prass M Goodman J Czelusniak L Y Chang J L Slightom 《Molecular biology and evolution》1984,1(5):371-389
Two fetal globin genes (G gamma and A gamma) from one chromosome of a
lowland gorilla (Gorilla gorilla gorilla) have been sequenced and compared
to three human loci (a G gamma-gene and two A gamma-alleles). A comparison
of regions of local homology among these five sequences indicates that long
after the duplication that produced the two nonallelic gamma-globin loci of
catarrhine primates, about 35 million years (Myr) ago, at least one gene
conversion event occurred between these loci. This conversion occurred not
long before the ancestral divergence (about 6 Myr ago) of Homo and Gorilla.
After this ancestral divergence, a minimum of three more gene conversion
events occurred in the human lineage. Each human A gamma-allele shares
specific sequence features with the gorilla A gamma-gene; one such
distinctive allelic feature involves the simple repeated sequence in IVS 2.
This suggests that early in the human lineage the A gamma-genes may have
undergone a crossing-over event mediated by this simple repeated sequence.
The DNA sequences from coding regions of both G gamma- and A gamma-loci, a
comparison of 292 codons in the corresponding gorilla and human genes, show
an unusually low evolutionary rate, with only two nonsilent differences
and, surprisingly, not even one silent substitution. The two nonsynonymous
substitutions observed predict a glycine at codon 73 and an arginine at
codon 104 in the gorilla A gamma-sequence rather than aspartic acid and
lysine, respectively, in human A gamma. Because only arginine has been
found at position 104 in gamma-chains of Old World monkeys, it may
represent the ancestral residue lost in gorilla and human G gamma-chains
and in the human A gamma-chain. Possibly the arginine codon (AGG) was
replaced by the lysine codon (AAG) in the G gamma-gene of a common ancestor
of Homo and Gorilla and then was transferred to the A gamma-gene by
subsequent conversions in the human lineage. DNA sequence conversions,
similar to that attributed to the fetal gamma-globin genes, appear to be
relatively frequent phenomena and, if widespread throughout the genome, may
have profound evolutionary consequences.
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Molecular history of gene conversions in the primate fetal gamma-globin genes. Nucleotide sequences from the common gibbon, Hylobates lar 总被引:7,自引:0,他引:7
Comparative and phylogenetic analyses of homologous sequences from closely related species reveal genetic events which have happened in the past and thus provide considerable insight into molecular genetic processes. One such process which has been especially important in the evolution of multigene families is gene conversion. The fetal gamma 1 and gamma 2-globin genes of catarrhine primates (humans, apes, and Old World monkeys) underwent numerous gene conversion events after they arose from a gene duplication event 25-35 million years ago. By including the gamma 1- and gamma 2-globin gene sequences from the common gibbon, Hylobates lar, the present work expands the gamma-globin data set to represent all major groups of hominoid primates. A computer-assisted algorithm is introduced which reveals converted DNA segments and provides results very similar to those obtained by site-by-site evolutionary reconstruction. Both methods provide strong evidence for at least 14 different converted stretches in catarrhine primates as well as five conversions in ancestral lineages. Features of gene conversions generalized from this molecular history are 1) conversions are restricted to regions maintaining high degrees of sequence similarity, 2) one gene may dominate in converting another gene, 3) sequences involved in conversions may accumulate changes more rapidly than expected, and 4) certain elements, such as polypurine/polypyrimidine [Y)n) and (TG)n elements, appear to be hotspots for initiating or terminating conversion events. 相似文献
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Rhesus fetal globin genes. Concerted gene evolution in the descent of higher primates 总被引:3,自引:0,他引:3
J L Slightom B F Koop P L Xu M Goodman 《The Journal of biological chemistry》1988,263(25):12427-12438
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F Ramirez A L Burns J G Mears S Spence D Starkman A Bank 《Nucleic acids research》1979,7(5):1147-1162
Three clones containing both the human G gamma and A gamma globlin genes have been isolated and characterized from a library of DNA fragments generated by partial Eco RI digestion of cellular DNA using charon 4A phage as vector. Two of the clones (NY 2 and 3) are identical and have an insert of 14.0 kb. The third clone (NY 1) has a 15.4 kb insert by virtue of an extra 1.4 kb Eco RI fragment at its 5' most end. This clone also has a Kpn I site not present in the other two suggesting it is the product of the gamma gene on the opposite chromosome. Restriction analysis of the three clones indicates that the G gamma and A gamma genes are linked on a single continuous piece of DNA and are separated by 3.5 kb and each contains at least one large intervening sequence of 0.85 kg between the Bam HI and Eco RI sites. These findings in cloned DNA provide direct evidence for linkage and organization of the gamma genes in man. 相似文献
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Chimpanzee fetal G gamma and A gamma globin gene nucleotide sequences provide further evidence of gene conversions in hominine evolution 总被引:5,自引:0,他引:5
The fetal globin genes G gamma and A gamma from one chromosome of a
chimpanzee (Pan troglodytes) were sequenced and found to be closely similar
to the corresponding genes of man and the gorilla. These genes contain
identical promoter and termination signals and have exons 1 and 2 separated
by the conserved short intron 1 (122 bp) and exons 2 and 3 separated by the
more rapidly evolving, larger intron 2 (893 bp and 887 bp in chimpanzee G
gamma and A gamma, respectively). Each intron 2 has a stretch of simple
sequence DNA (TG)n serving possibly as a "hot spot" for recombination. The
two chimpanzee genes encode polypeptide chains that differ only at position
136 (glycine in G gamma and alanine in A gamma) and that are identical to
the corresponding human chains, which have aspartic acid at position 73 and
lysine at 104 in contrast to glycine and arginine at these respective
positions of the gorilla A gamma chain. Phylogenetic analysis by the
parsimony method revealed four silent (synonymous) base substitutions in
evolutionary descent of the chimpanzee G gamma and A gamma codons and none
in the human and gorilla codons. These Homininae (Pan, Homo, Gorilla)
coding sequences evolved at one-tenth the average mammalian rate for
nonsynonymous and one-fourth that for synonymous substitutions. Three
sequence regions that were affected by gene conversions between chimpanzee
G gamma and A gamma loci were identified: one extended 3' of the hot spot
with G gamma replaced by the A gamma sequence, another extended 5' of the
hot spot with A gamma replaced by G gamma, and the third conversion
extended from the 5' flanking to the 5' end of intron 2, with G gamma
replaced here by the A gamma sequence. A conversion similar to this third
one has occurred independently in the descent of the gorilla genes. The
four previously identified conversions, labeled C1-C4 (Scott et al. 1984),
were substantiated with the addition of the chimpanzee genes to our
analysis (C1 being shared by all three hominines and C2, C3, and C4 being
found only in humans). Thus, the fetal genes from all three of these
hominine species have been active in gene conversions during the descent of
each species.
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The nucleotide sequences of the Klebsiella pneumoniae lacI and lacZ genes and part of the lacY gene were determined, and these genes were located and oriented relative to one another. The K. pneumoniae lac operon is divergent in that the lacI and lacZ genes are oriented head to head, and complementary strands are transcribed. Besides base substitutions, the lacZ genes of K. pneumoniae and Escherichia coli have suffered short distance shifts of reading frame caused by additions or deletions or both during evolutionary divergence from a common ancestral gene. Relative to corresponding E. coli sequences, the nucleotide sequences of the lacZ and lacY genes are 61 and 67% conserved, and the lacI genes are 49% conserved. A comparison of both nucleotide and amino acid sequences revealed that the K. pneumoniae and E. coli lacI genes and lac repressor proteins each are related to the galR gene and gal repressor of E. coli to about the same extent. In terms of evolutionary relationships, the divergence of the forerunner of the galR gene from an ancestral lac repressor gene preceded separation and differentiation of the K. pneumoniae and E. coli lac repressor genes. 相似文献
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Nucleotide sequence of 3'' untranslated portion of human alpha globin mRNA. 总被引:9,自引:4,他引:5
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J T Wilson J K deRiel B G Forget C A Marotta S M Weissman 《Nucleic acids research》1977,4(7):2353-2368
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A composite transposon 3'' to the cow fetal globin gene binds a sequence specific factor. 总被引:2,自引:2,他引:0
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Two unusual sequence organizations were found within the beta-globin locus of the cow. Each was a composite, consisting of closely linked Alu-type repeats with a short stretch of genomic non-repetitive sequence, called a lagan, sandwiched between. One lagan was found 3' to the fetal globin gene, while the second lay between the adult globin gene and a globin pseudogene. Southern blot analysis indicated that both lagans appeared twice within the cow haploid genome, with the second copies lying outside the cow beta-globin locus. One of these non-globin locus homologues was cloned and subjected to sequence analysis. Comparison of the DNA sequence data showed that the lagan-Alu composite was transposed as a unit. The lagan 3' to the cow fetal globin gene contains the recognition site for a sequence specific DNA binding factor. This factor was present in extracts from fetal, but not from adult cow tissues. 相似文献
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The nucleotide sequence of the DNA fragment containing the beta-glucosidase gene of Candida pelliculosa was determined. Analysis of the sequence revealed three open reading frames which could encode 65,825, and 412 amino acid residues. The presence of the second frame was found to be sufficient for the expression of the beta-glucosidase gene in a heterologous host Saccharomyces cerevisiae. Putative protein encoded by this gene had hydrophobic amino acids, resembling a signal peptide, at its N-terminal region and 19 potential glycosylation sites. Codon usage of Candida genes had the similar pattern shown in S.cerevisiae. Codon bias of the beta-glucosidase gene of Candida was relatively low, compared with that of the highly expressed genes of S. cerevisiae. 相似文献
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