共查询到20条相似文献,搜索用时 15 毫秒
1.
V.V. Grechko L.V. Fedorova A.N. Fedorov S.Ya. Slobodyanyuk D.M. Ryabinin M.N. Melnikova A.A. Bannikova A.A. Lomov V.A. Sheremet'eva V.A. Gorshkov G.A. Sevostyanova S.K. Semenova A.P. Ryskov B.M. Mednikov I.S. Darevsky 《Journal of molecular evolution》1997,45(3):332-336
Multiple band patterns of DNA repeats in the 20–500-nucleotide range can be detected by digesting genomic DNA with short—cutting
restriction endonucleases, followed by end labeling of the restriction fragments and fractionation in nondenaturing polyacrylamide
gels. We call such band patterns obtained from genomic DNA ``taxonprints' (Fedorov et al. 1992). Here we show that taxonprints
for the taxonomic groups studied (mammals, reptiles, fish, insects—altogether more than 50 species) have the following properties:
(1) All individuals from the same species have identical taxonprints. (2) Taxonprint bands can be subdivided into those specific
for a single species and those specific for groups of closely related species, genera, and even families. (3) Each restriction
endonuclease produces unique band patterns; thus, five to ten restriction enzymes (about 100 bands) may be sufficient for
a statistical treatment of phylogenetic relationships based on polymorphisms of restriction endinuclease sites. We demonstrate
that taxonprint analysis allows one to distinguish closely related species and to establish the degree of similarity among
species and among genera. These characteristics make taxonprint analysis a valuable tool for taxonomic and phylogenetic studies.
Received: 10 February 1997 / Accepted: 10 March 1997 相似文献
2.
Chromosome terminal, complex repeats in the dipteran Chironomus pallidivittatus show rapid concerted evolution during which there is remarkably efficient homogenization of the repeat units within and between
chromosome ends. It has been shown previously that gene conversion is likely to be an important component during these changes.
The sequence evolution could be a result of different processes—exchanges between repeats in the tandem array as well as information
transfer between units in different chromosomes—and is therefore difficult to analyze in detail. In this study the concerted
evolution of a region present only once per chromosome, at the junction between the telomeric complex repeats and the subtelomeric
DNA was therefore investigated in the two sibling species C. pallidivittatus and C. tentans. Material from individual microdissected chromosome ends was used, as well as clones from bulk genomic DNA. On the telomeric
side of the border pronounced species-specific sequence differences were observed, the patterns being similar for clones of
different origin within each species. Mutations had been transmitted efficiently between chromosomes also when adjoining,
more distally localized DNA showed great differences in sequence, suggesting that gene conversion had taken place. The evolving
telomeric region bordered proximally to subtelomeric DNA with high evolutionary constancy. More proximally localized, subtelomeric
DNA evolved more rapidly and showed heterogeneity between species and chromosomes.
Received: 24 September 1997 / Accepted: 24 November 1997 相似文献
3.
Dorothy E. Pumo Peter S. Finamore William R. Franek Carleton J. Phillips Sima Tarzami Darlene Balzarano 《Journal of molecular evolution》1998,47(6):709-717
The complete mitochondrial genome was obtained from a microchiropteran bat, Artibeus jamaicensis. The presumptive amino acid sequence for the protein-coding genes was compared with predicted amino acid sequences from several
representatives of other mammalian orders. Data were analyzed using maximum parsimony, maximum likelihood, and neighbor joining.
All analyses placed bats as the sister group of carnivores, perissodactyls, artiodactyls, and cetaceans (e.g., 100% bootstrap
value with both maximum parsimony and neighbor joining). The data strongly support a new hypothesis about the origin of bats,
specifically a bat/ferungulate grouping. None of the analyses supported the superorder Archonta (bats, flying lemurs, primates,
and tree shrews). Our hypothesis regarding the relationship of bats to other eutherian mammals is concordant with previous
molecular studies and contrasts with hypotheses based solely on morphological criteria and an incomplete fossil record. The
A. jamaicensis mitochondrial DNA control region has a complex pattern of tandem repeats that differs from previously reported chiropteran
control regions.
Received: 22 January 1998 / Accepted: 3 June 1998 相似文献
4.
Microsatellite length variation was investigated at a highly variable microsatellite locus in four species of Apodemus. Information obtained from microsatellite allele sequences was contrasted with allele sizes, which included 18 electromorphs.
Additional analysis of a 400-bp unique sequence in the flanking region identified 26 different haplotype sequences or ``true'
alleles in the sample. Three molecular mechanisms, namely, (1) addition/deletion of repeats, (2) substitutions and indels
in the flanking region, and (3) mutations interrupting the repeat, contributed to the generation of allelic variation. Size
homoplasy can be inferred for alleles within populations, from different populations of the same species, and from different
species. We propose that microsatellite flanking sequences may be informative markers for investigating mutation processes
in microsatellite repeats as well as phylogenetic relationships among alleles, populations, and species.
Received: 3 November 1999 / Accepted: 2 May 2000 相似文献
5.
We examined the evolution of the repeat regions of three noncoding microsatellite loci in 58 species of the Polistinae, a
subfamily of wasps that diverged over 140 million years ago. A phylogenetic approach allows two new kinds of approaches to
studying microsatellite evolution: character mapping and comparative analysis. The basic repeat structure of the loci was
highly conserved, but was often punctuated with imperfections that appear to be phylogenetically informative. Repeat numbers
evolved more rapidly than other changes in the repeat region. Changes in number of repeats among species seem consistent with
the stepwise mutation model, which is based on slippage during replication as the main source of mutations. Changes in repeat
numbers can occur even when there are very few tandem repeats but longer repeats, especially perfect repeats led to greater
rates of evolutionary change. Species phylogenetically closer to the one from which we identified the loci had longer stretches
of uninterrupted repeats and more different motifs, but not longer total repeat regions. The number of perfect repeats increased
more often than it decreased. However, there was no evidence that some species have consistently greater numbers of repeats
across loci than other species have, once ascertainment bias is eliminated. We also found no evidence for a population size
effect posited by one form of the directionality hypothesis. Overall, phylogenetic variation in repeat regions can be explained
by adding neutral evolution to what is already known about the mutation process. The life cycle of microsatellites appears
to reflect a balance between growth by slippage and degradation by an essentially irreversible accumulation of imperfections.
Received: 13 April 1999 / Accepted: 8 September 1999 相似文献
6.
The intriguing diversity of highly abundant satellite repeats found even among closely related species can result from processes
leading to dramatic changes in copy number of a particular sequence in the genome and not from rapid accumulation of mutations.
To test this hypothesis, we investigated the distribution of the PRAT satellite DNA family, a highly abundant major satellite
in the coleopteran species Palorus ratzeburgii, in eight species belonging to the related genera (Tribolium, Tenebrio, Latheticus), the subfamily (Pimeliinae), and the family (Chrysomelidae). Dot blot analysis and PCR assay followed by Southern hybridization
revealed that the PRAT satellite, in the form of low-copy number repeats, was present in all tested species. The PRAT satellite
detected in the species Pimelia elevata has been sequenced, and compared with previously cloned PRAT monomers from Palorus ratzeburgii and Palorus subdepressus. Although the two Palorus species diverged at least 7 Myr ago, and the subfamily Pimeliinae separated from the genus Palorus 50–60 Myr ago, all PRAT clones exhibit high mutual homology, with average variability relative to the common consensus sequence
of 1.3%. The presence of ancestral mutations found in PRAT clones from all three species as well as the absence of species
diagnostic mutations illustrate extremely slow sequence evolution. This unexpectedly high conservation of PRAT satellite DNA
sequence might be induced by a small bias of turnover mechanisms favoring the ancestral sequence in the process of molecular
drive. 相似文献
7.
Base Composition Skews, Replication Orientation, and Gene Orientation in 12 Prokaryote Genomes 总被引:21,自引:0,他引:21
Michael J. McLean Kenneth H. Wolfe Kevin M. Devine 《Journal of molecular evolution》1998,47(6):691-696
Variation in GC content, GC skew and AT skew along genomic regions was examined at third codon positions in completely sequenced
prokaryotes. Eight out of nine eubacteria studied show GC and AT skews that change sign at the origin of replication. The
leading strand in DNA replication is G-T rich at codon position 3 in six eubacteria, but C-T rich in two Mycoplasma species. In M. genitalium the AT and GC skews are symmetrical around the origin and terminus of replication, whereas its GC content variation has been
shown to have a centre of symmetry elsewhere in the genome. Borrelia burgdorferi and Treponema pallidum show extraordinary extents of base composition skew correlated with direction of DNA replication. Base composition skews
measured at third codon positions probably reflect mutational biases, whereas those measured over all bases in a sequence
(or at codon positions 1 and 2) can be strongly affected by protein considerations due to the tendency in some bacteria for
genes to be transcribed in the same direction that they are replicated. Consequently in some species the direction of skew
for total genomic DNA is opposite to that for codon position 3.
Received: 2 February 1998 / Accepted: 15 June 1998 相似文献
8.
A DNA fragment containing short tandem repeat sequences (approximately 86-bp repeat) was isolated from a Xenopus laevis cDNA library. Southern blot and in situ hybridization analyses revealed that the repeat was highly dispersed in the genome and was present at approximately 1 million
copies per haploid genome. We named this element Xstir (Xenopus short tandemly and invertedly repeating element) after its arrangement in the genome. The majority of the genomic Xstir sequences
were digested to monomer and dimer sizes with several restriction enzymes. Their sequences were found to be highly homogeneous
and organized into tandem arrays in the genome. Alignment analyses of several known sequences showed that some of the Xstir-like
sequences were also organized into interspersed inverted repeats. The inverted repeats consisted of an inverted pair of two
differently modified Xstirs separated by a short insert. In addition, these were framed by another novel inverted repeat (Xstir-TIR).
The Xstir-TIR sequence was also found at the ends of tandem Xstir arrays. Furthermore, we found that Xstir-TIR was linked
to a motif characterizing the T2 family which belonged to a vertebrate MITE (miniature inverted-repeat transposable element)
family, suggesting the importance of Xstir-TIR for their amplification and transposition. The present study of 11 anuran and
2 urodele species revealed that Xstir or Xstir-like sequences were extensively amplified in the three Xenopus species. Genomic Xstir populations of X. borealis and X. laevis were mutually indistinguishable but significantly different from that of X. tropicalis.
Received: 5 April 2000 / Accepted: 3 August 2000 相似文献
9.
Sybille Kubis John Seymour Heslop-Harrison Thomas Schmidt 《Journal of molecular evolution》1997,44(3):310-320
Members of a highly abundant restriction satellite family have been isolated from the wild beet species Beta nana. The satellite DNA sequence is characterized by a conserved RsaI restriction site and is present in three of four sections of the genus Beta, namely Nanae, Corollinae, and Beta. It was not detected in species of the evolutionary old section Procumbentes, suggesting its amplification after separation of this section. Sequences of eight monomers were aligned revealing a size
variation from 209 to 233 bp and an AT content ranging from 56.5% to 60.5%. The similarity between monomers in B. nana varied from 77.7% to 92.2%. Diverged subfamilies were identified by sequence analysis and Southern hybridization. A comparative
study of this repetitive DNA element by fluorescent in situ hybridization and Southern analyses in three representative species
was performed showing a variable genomic organization and heterogeneous localizations along metaphase chromosomes both within
and between species. In B. nana the copy number of this satellite, with some 30,000 per haploid genome, is more than tenfold higher than in Beta lomatogona and up to 200 times higher than in Beta vulgaris, indicating different levels of sequence amplification during evolution in the genus Beta. In sugar beet (B. vulgaris), the large-scale organization of this tandem repeat was examined by pulsed-field gel electrophoresis. Southern hybridization
to genomic DNA digested with DraI demonstrated that satellite arrays are located in AT-rich regions and the tandem repeat is a useful probe for the detection
of genetic variation in closely related B. vulgaris cultivars, accessions, and subspecies.
Received: 24 May 1996 / Accepted: 13 September 1996 相似文献
10.
PCR-RFLP analysis of cpDNA in the genus Abies 总被引:1,自引:0,他引:1
L. Parducci A. E. Szmidt 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,98(5):802-808
We used PCR-RFLP analysis of the chloroplast DNA of the genus Abies (family Pinaceae), to determine if the method could be employed to detect inter-specific variation in this genus and to study how the variation
was distributed in different regions of the genome. Ten different chloroplast DNA regions, consisting of coding and non-coding
DNA sequences, were amplified with specific primers in ten different Abies taxa. The amplification products were digested with several restriction enzymes. The results showed that the chloroplast
genome is highly variable in most of the investigated taxa and contains multiple variable regions that appear to be distributed
throughout the whole genome. Species-diagnostic markers were found for four of the ten investigated species. Unexpectedly,
intra-specific variation was also detected in four species. It is likely that further studies, including larger sample sizes
and/or more powerful methods for the detection of chloroplast DNA variation, will reveal additional variation for this genus.
Received: 2 September 1998 / Accepted: 17 September 1998 相似文献
11.
Sequence data of mitochondrial 16S ribosomal DNA (mt-rDNA) and nuclear 28S ribosomal DNA (nuc-rDNA) were compared in two
honeybee species (Apis mellifera and Apis dorsata) and a selection of 22 wasp species (Vespidae) with different levels of sociality. The averge substitution rates in mt-rDNA
and nuc-rDNA were almost-equal in solitary species. In species with larger nests, however, the difference between the nuclear
and the mitochondrial substitution rate significantly increased. The average substitution ratio, ψ (nucleotide substitutions
in mt-rDNA/nucleotide substitutions in nuc-rDNA) was 1.48 ± 0.12 (SE) among the solitary Eumeninae, 3.70 ± 0.15 among five
primitive social Stenogastrinae species, 3.24 ± 0.20 among five Polistinae species, 5.76 ± 0.33 among nine highly eusocial
Vespinae, and 12.7 in the two Apis species. The high egg-laying rate and the effective population size skew between the sexes may contribute to the rise of
the substitution ratio in the highly eusocial species. Drift and bottleneck effects in the mitochondrial DNA pool during speciation
events as well as polyandry may further enhance this phenomenon.
Received: 12 January 1998 / Accepted: 28 April 1998 相似文献
12.
Eduardo Eizirik Sandro L. Bonatto Warren E. Johnson Peter G. Crawshaw Jr. Jean Cristophe Vié Dulce M. Brousset Stephen J. O'Brien Francisco M. Salzano 《Journal of molecular evolution》1998,47(5):613-624
The ocelot (Leopardus pardalis) and margay (L. wiedii) are sister-species of Neotropical cats which evolved from a lineage that migrated into South America during the formation
of the Panamanian land bridge 3–5 million years ago. Patterns of population genetic divergence of each species were studied
by phylogenetic analyses of mitochondrial DNA (mtDNA) control region sequences in individuals sampled across the distribution
of these taxa. Abundant genetic diversity and remarkably concordant phylogeographic partitions for both species were observed,
identifying parallel geographic regions which likely reflect historical faunal barriers. Inferred aspects of phylogeography,
population genetic structure, and demographic history were used to formulate conservation recommendations for these species.
In addition, observed patterns of sequence variation provided insight into the molecular evolution of the mtDNA control region
in closely related felids.
Received: 26 January 1998 / Accepted: 14 May 1998 相似文献
13.
A mitochondrial DNA (mtDNA) phylogeny of cichlid fish is presented for the most taxonomically inclusive data set compiled
to date (64 taxa). 16S rDNA data establish with confidence relationships among major lineages of cichlids, with a general
pattern congruent with previous morphological studies and less inclusive molecular phylogenies based on nuclear genes. Cichlids
from Madagascar and India are the most basal groups of the family Cichlidae and sister to African–Neotropical cichlids. The
cichlid phylogeny suggests drift-vicariance events, consistent with the fragmentation of Gondwana, to explain current biogeographic
distributions. Important phylogenetic findings include the placement of the controversial genus Heterochromis basal among African cichlids, the South American genus Retroculus as the most basal taxon of the Neotropical cichlid assemblage, and the close relationship of the Neotropical genera Cichla with Astronotus rather than with the crenicichlines. Based on a large number of South American genera, the Neotropical cichlids are defined
as a monophyletic assemblage and shown to harbor significantly higher levels of genetic variation than their African counterparts.
Relative rate tests suggest that Neotropical cichlids have experienced accelerated rates of molecular evolution. But these
high evolutionary rates were significantly higher among geophagine cichlids.
Received: 18 September 1998 / Accepted: 16 December 1998 相似文献
14.
Tandemly repeated sequences are a major component of the eukaryotic genome. Although the general characteristics of tandem
repeats have been well documented, the processes involved in their origin and maintenance remain unknown. In this study, a
region on the paternal sex ratio (PSR) chromosome was analyzed to investigate the mechanisms of tandem repeat evolution. The
region contains a junction between a tandem array of PSR2 repeats and a copy of the retrotransposon NATE, with other dispersed repeats (putative mobile elements) on the other side of the element. Little similarity was detected
between the sequence of PSR2 and the region of NATE flanking the array, indicating that the PSR2 repeat did not originate from the underlying NATE sequence. However, a short region of sequence similarity (11/15 bp) and an inverted region of sequence identity (8 bp) are
present on either side of the junction. These short sequences may have facilitated nonhomologous recombination between NATE and PSR2, resulting in the formation of the junction. Adjacent to the junction, the three most terminal repeats in the PSR2
array exhibited a higher sequence divergence relative to internal repeats, which is consistent with a theoretical prediction
of the unequal exchange model for tandem repeat evolution. Other NATE insertion sites were characterized which show proximity to both tandem repeats and complex DNAs containing additional dispersed
repeats. An ``accretion model' is proposed to account for this association by the accumulation of mobile elements at the
ends of tandem arrays and into ``islands' within arrays. Mobile elements inserting into arrays will tend to migrate into
islands and to array ends, due to the turnover in the number of intervening repeats.
Received: 18 August 1997 / Accepted: 18 September 1998 相似文献
15.
We have examined the length distribution of perfect dimer repeats, where perfect means uninterrupted by any other base, using
data from GenBank on primates and rodents. Virtually no lengths greater than 30 repeats are found, except for rodent AG repeats,
which extend to 35. Comparable numbers of long AC and AG repeats suggest that they have not been selected for special functions
or DNA structures. We have compared the data with predictions of two models: (1) a Bernoulli Model in which bases are assumed
equally likely and distributed at random and (2) an Unbiased Random Walk Model (URWM) in which repeats are permitted to change
length by plus or minus one unit, with equal probabilities, and in which base substitutions are allowed to destroy long perfect
repeats, producing two shorter perfect repeats. The source of repeats is assumed to be from single base substutions from neighboring
sequences, i.e., those differing from the perfect repeat by a single base. Mutation rates either independent of repeat length
or proportional to length were considered. An upper limit to the lengths L≈ 30 is assumed and isolated dimers are assumed unable to expand, so that there are absorbing barriers to the random walk
at lengths 1 and L+ 1, and a steady state of lengths is reached. With these assumptions and estimated values for the rates of length mutation
and base substitution, reasonable agreement is found with the data for lengths > 5 repeats. Shorter repeats, of lengths ≤
3 are in general agreement with the Bernoulli Model. By reducing the rate of length mutations for n≤ 5, it is possible to obtain reasonable agreement with the full range of data. For these reduced rates, the times between
length mutations become comparable to those suggested for a bottleneck in the evolution of Homo sapiens, which may be the reason for low heterozygosity of short repeats. 相似文献
16.
We studied the expression, distribution, and phosphorylation of the tight junction (TJ) protein occludin in confluent MDCK
cell monolayers following three procedures for opening and resealing of TJs. When Ca2+ is transiently removed from the culture medium, the TJs open and the cells separate from each other, but the occludin band
around each cell is retained. When Ca2+ is reintroduced, the TJs reseal. When the monolayers are exposed to prolonged Ca2+ starvation the cells maintain contact, but occludin disappears from the cell borders and can be detected only in a cytoplasmic
compartment. When Ca2+ is reintroduced, new TJs are assembled and the transepithelial electrical resistance (TER) is reestablished in about 20 hr.
Monolayers treated with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) show a different pattern of TJ opening:
the cell-cell contact is maintained but the TJ strand network, as seen in freeze-fracture replicas, becomes discontinuous.
Occludin is still localized at the cell periphery, but in a pattern of distribution that matches the discontinuous TJ. These
TJs do not reseal even 24 hr after removal of the TPA. Western blot analysis showed that the 62–65 kD double band of occludin
did not change with these treatments. However, in vivo phosphorylation analysis showed that the TPA treatment reduced the
phosphorylation levels of occludin, while the prolonged Ca2+ starvation completely dephosphorylated the two occludin bands. In addition, a highly phosphorylated 71 kD band that immunoprecipitates
with occludin is not present when TJ is opened by the Ca2+ removal. Phosphoaminoacid analysis showed that the 62–65 kD occludin bands are phosphorylated on serine and threonine, while
the 71 kD band was phosphorylated exclusively on serine. Our results provide further evidence that phosphorylation of occludin
is an important step in regulating TJ formation and permeability.
Received: 28 December 1998/Revised: 8 April 1999 相似文献
17.
A long repetitive DNA sequence (OtY8) has been cloned from male chinook salmon and its genomic organization has been characterized.
The repeat has a unit length of 8 kb and is present approximately 300 times per diploid male nucleus. All internal fragments
within the 8-kb repeat segregate from father to son, suggesting that the entire repeat unit is located on the Y chromosome.
The organization of this sequence into an 8-kb repeat unit is restricted to the Y chromosome, as are several male-specific
repeat subtypes identified on the basis of restriction-site variation. The repeat possesses only weak internal sequence similarities,
suggesting that OtY8 has not arisen by duplication of a smaller repeat unit, as is the case for other long tandem arrays found
in eukaryotes. Based on a laddered pattern arising from partial digestion of genomic DNA with a restriction enzyme which cuts
only once per repeat unit, this sequence is not dispersed on the Y chromosome but is organized as a head-to-tail tandem array.
Pulse-gel electrophoresis reveals that the direct-tandem repeats are organized into at least six separate clusters containing
approximately 12 to 250 copies, comprising some 2.4 Mb of Y-chromosomal DNA in total. Related sequences with nucleotide substitutions
and DNA insertions relative to the Y-chromosomal fragment are found elsewhere in the genome but at much lower copy number
and, although similar sequences are also found in other salmonid species, the amplification of the repeat into a Y-chromosome-linked
tandem array is only observed in chinook salmon. The OtY8 repetitive sequence is genetically tightly associated with the sex-determination
locus and provides an opportunity to examine the evolution of the Y chromosome and sex determination process in a lower vertebrate.
Received: 4 April 1997 / Accepted: 22 July 1997 相似文献
18.
We harvested canalicular-enriched plasma membranes of hepatocytes and collected fistula bile from male rats and isolated
the sphingomyelins. Following sphingomyelinase hydrolysis, we identified the sphingomyelin molecular species on the basis
of their benzoylated ceramide derivatives employing high performance liquid chromatography. Sphingomyelin constitutes ≤3%
of total biliary phospholipids (which are mostly sn-1 16:0 long-chain phosphatidylcholines) and approximately 30% of canalicular-enriched
membranes. In both cases, the principal molecular species were composed of 16:0, 18:0, 20:0, 22:0, 23:0, 24:0, 24:1 and 24:2
fatty acid classes. However, the 16:0 fatty acid species was enriched in biliary sphingomyelin to a significantly greater
degree than in sphingomyelins of canalicular-enriched plasma membranes (46% vs. 25% of total). We argue a physical-chemical case for laterally separated domains of very long chain sphingomyelins on the
exoplasmic leaflet of the canalicular membrane. We bolster our hypothesis by the likelihood that the least hydrophobic, e.g.,
16:0 sphingomyelin molecular species, are miscible with biliary phosphatidylcholines, and are secreted into bile. Laterally
separated domains of very long chain sphingomyelins on the exoplasmic leaflet of the canalicular membrane could provide a
means of sequestering cholesterol molecules prior to secretion into bile.
Received: 19 March 1998/Revised: 8 October 1998 相似文献
19.
20.
Masaharu Takemura 《Journal of molecular evolution》2001,52(5):419-425
A number of molecular forms of DNA polymerases have been reported to be involved in eukaryotic nuclear DNA replication, with
contributions from α-, δ-, and ε-polymerases. It has been reported that δ-polymerase possessed a central role in DNA replication
in archaea, whose ancestry are thought to be closely related to the ancestor of eukaryotes. Indeed, in vitro experiment shown
here suggests that δ-polymerase has the potential ability to start DNA synthesis immediately after RNA primer synthesis. Therefore,
the question arises, where did the α-polymerase come from? Phylogenetic analysis based on the nucleotide sequence of several
conserved regions reveals that two poxviruses, vaccinia and variola viruses, have polymerases similar to eukaryotic α-polymerase
rather than δ-polymerase, while adenovirus, herpes family viruses, and archaeotes have eukaryotic δ-like polymerases, suggesting
that the eukaryotic α-polymerase gene is derived from a poxvirus-like organism, which had some eukaryote-like characteristics.
Furthermore, the poxvirus's proliferation independent from the host-cell nucleus suggests the possibility that this virus
could infect non-nucleated cells, such as ancestral eukaryotes. I wish to propose here a new hypothesis for the origin of
the eukaryotic nucleus, posing symbiotic contact of an orthopoxvirus ancestor with an archaebacterium, whose genome already
had a δ-like polymerase gene.
Received: 26 October 2000 / Accepted: 16 January 2001 相似文献