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Homologous recombination occurs frequently at innate GT microsatellites in normal somatic and germ cells in vivo. BMC Genomics 2018; 19:359. [PMID: 29751739 PMCID: PMC5948810 DOI: 10.1186/s12864-018-4758-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Accepted: 05/03/2018] [Indexed: 12/30/2022] Open
Abstract
Background In somatic cells, homologous recombination (HR) is a rare event caused by eventual DNA double-strand breaks (DSBs). In contrast, germ cells show high frequency of HR caused by programmed DSBs. Microsatellites are prone to DSBs during genome replication and, thereby, capable of promoting HR. It remains unclear whether HR occurs frequently at microsatellites both in normal somatic cells and germ cells in a similar manner. Results By examining the linkage pattern of multiple paternal and maternal markers flanking innate GT microsatellites, we measured HR at the GT microsatellites in various somatic cells and germ cells in a goldfish intraspecific heterozygote. During embryogenesis, the HR products accumulate gradually with the increase of the number of cell divisions. The frequency of HR at the GT microsatellites in advanced embryos, adult tissues and germ cells is surprisingly high. The type of exchanges between the homologous chromosomes is similar in normal advanced embryos and germ cells. Furthermore, a long GT microsatellite is more active than a short one in promoting HR in both somatic and germ cells. Conclusions HR occurs frequently at innate GT microsatellites in normal somatic cells and germ cells in a similar manner. Electronic supplementary material The online version of this article (10.1186/s12864-018-4758-y) contains supplementary material, which is available to authorized users.
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Minimum length of direct repeat sequences required for efficient homologous recombination induced by zinc finger nuclease in yeast. Mol Biol Rep 2014; 41:6939-48. [DOI: 10.1007/s11033-014-3579-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Accepted: 07/01/2014] [Indexed: 10/25/2022]
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Kejnovský E, Michalovova M, Steflova P, Kejnovska I, Manzano S, Hobza R, Kubat Z, Kovarik J, Jamilena M, Vyskot B. Expansion of microsatellites on evolutionary young Y chromosome. PLoS One 2013; 8:e45519. [PMID: 23341866 PMCID: PMC3547029 DOI: 10.1371/journal.pone.0045519] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Accepted: 08/20/2012] [Indexed: 01/30/2023] Open
Abstract
Sex chromosomes are an ideal system to study processes connected with suppressed recombination. We found evidence of microsatellite expansion, on the relatively young Y chromosome of the dioecious plant sorrel (Rumex acetosa, XY1Y2 system), but no such expansion on the more ancient Y chromosomes of liverwort (Marchantia polymorpha) and human. The most expanding motifs were AC and AAC, which also showed periodicity of array length, indicating the importance of beginnings and ends of arrays. Our data indicate that abundance of microsatellites in genomes depends on the inherent expansion potential of specific motifs, which could be related to their stability and ability to adopt unusual DNA conformations. We also found that the abundance of microsatellites is higher in the neighborhood of transposable elements (TEs) suggesting that microsatellites are probably targets for TE insertions. This evidence suggests that microsatellite expansion is an early event shaping the Y chromosome where this process is not opposed by recombination, while accumulation of TEs and chromosome shrinkage predominate later.
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Affiliation(s)
- Eduard Kejnovský
- Department of Plant Developmental Genetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, Brno, Czech Republic.
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Guo WJ, Ling J, Li P. Consensus features of microsatellite distribution: Microsatellite contents are universally correlated with recombination rates and are preferentially depressed by centromeres in multicellular eukaryotic genomes. Genomics 2009; 93:323-31. [DOI: 10.1016/j.ygeno.2008.12.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2008] [Revised: 12/14/2008] [Accepted: 12/16/2008] [Indexed: 10/21/2022]
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Holloway K, Lawson VE, Jeffreys AJ. Allelic recombination and de novo deletions in sperm in the human beta-globin gene region. Hum Mol Genet 2006; 15:1099-111. [PMID: 16501000 DOI: 10.1093/hmg/ddl025] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Meiotic recombination is of fundamental importance in creating haplotype diversity in the human genome and has the potential to cause genomic rearrangements by ectopic recombination between repeat sequences and through other changes triggered by recombination-initiating events. However, the relationship between allelic recombination and genome instability in the human germline remains unclear. We have therefore analysed recombination and DNA instability in the delta-, beta-globin gene region and its associated recombination hotspot. Sperm typing has for the first time accurately defined the hotspot and shown it to be the most active autosomal crossover hotspot yet described, although unusually inactive in non-exchange gene conversion. The hotspot just extends into a homology block shared by the delta- and beta-globin genes, within which ectopic exchanges can generate Hb Lepore deletions. We developed a physical selection method for recovering and validating extremely rare de novo deletions in human DNA and used it to characterize the dynamics of these Hb Lepore deletions in sperm as well as other deletions not arising from ectopic exchanges between homologous DNA sequences. Surprisingly, both classes of deletion showed breakpoints that avoided the beta-globin hotspot, establishing that it possesses remarkable fidelity and does not play a significant role in triggering these DNA rearrangements. This study also provides the first direct analysis of de novo deletion in the human germline and points to a possible deletion-controlling element in the beta-globin gene separate from the crossover hotspot.
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Affiliation(s)
- Kim Holloway
- Department of Genetics, University of Leicester, Leicester LE1 7RH, UK
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Li YC, Korol AB, Fahima T, Beiles A, Nevo E. Microsatellites: genomic distribution, putative functions and mutational mechanisms: a review. Mol Ecol 2002; 11:2453-65. [PMID: 12453231 DOI: 10.1046/j.1365-294x.2002.01643.x] [Citation(s) in RCA: 601] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Microsatellites, or tandem simple sequence repeats (SSR), are abundant across genomes and show high levels of polymorphism. SSR genetic and evolutionary mechanisms remain controversial. Here we attempt to summarize the available data related to SSR distribution in coding and noncoding regions of genomes and SSR functional importance. Numerous lines of evidence demonstrate that SSR genomic distribution is nonrandom. Random expansions or contractions appear to be selected against for at least part of SSR loci, presumably because of their effect on chromatin organization, regulation of gene activity, recombination, DNA replication, cell cycle, mismatch repair system, etc. This review also discusses the role of two putative mutational mechanisms, replication slippage and recombination, and their interaction in SSR variation.
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Affiliation(s)
- You-Chun Li
- Institute of Evolution, University of Haifa, Haifa 31905, Israel
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Pluciennik A, Iyer RR, Napierala M, Larson JE, Filutowicz M, Wells RD. Long CTG.CAG repeats from myotonic dystrophy are preferred sites for intermolecular recombination. J Biol Chem 2002; 277:34074-86. [PMID: 12087090 DOI: 10.1074/jbc.m202127200] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Homologous recombination was shown to enable the expansion of CTG.CAG repeat sequences. Other prior investigations revealed the involvement of replication and DNA repair in these genetic instabilities. Here we used a genetic assay to measure the frequency of homologous intermolecular recombination between two CTG.CAG tracts. When compared with non-repeating sequences of similar lengths, long (CTG.CAG)(n) repeats apparently recombine with an approximately 60-fold higher frequency. Sequence polymorphisms that interrupt the homogeneity of the CTG.CAG repeat tracts reduce the apparent recombination frequency as compared with the pure uninterrupted repeats. The orientation of the repeats relative to the origin of replication strongly influenced the apparent frequency of recombination. This suggests the involvement of DNA replication in the recombination process of triplet repeats. We propose that DNA polymerases stall within the CTG.CAG repeat tracts causing nicks or double-strand breaks that stimulate homologous recombination. The recombination process is RecA-dependent.
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Affiliation(s)
- Anna Pluciennik
- Institute of Biosciences and Technology, Center for Genome Research, Texas A & M University System Health Science Center, Texas Medical Center, 2121 W. Holcombe Boulevard, Houston, TX 77030, USA
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Lambert S, Saintigny Y, Delacote F, Amiot F, Chaput B, Lecomte M, Huck S, Bertrand P, Lopez BS. Analysis of intrachromosomal homologous recombination in mammalian cell, using tandem repeat sequences. Mutat Res 1999; 433:159-68. [PMID: 10343649 DOI: 10.1016/s0921-8777(99)00004-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
In all the organisms, homologous recombination (HR) is involved in fundamental processes such as genome diversification and DNA repair. Several strategies can be devised to measure homologous recombination in mammalian cells. We present here the interest of using intrachromosomal tandem repeat sequences to measure HR in mammalian cells and we discuss the differences with the ectopic plasmids recombination. The present review focuses on the molecular mechanisms of HR between tandem repeats in mammalian cells. The possibility to use two different orientations of tandem repeats (direct or inverted repeats) in parallel constitutes also an advantage. While inverted repeats measure only events arising by strand exchange (gene conversion and crossing over), direct repeats monitor strand exchange events and also non-conservative processes such as single strand annealing or replication slippage. In yeast, these processes depend on different pathways, most of them also existing in mammalian cells. These data permit to devise substrates adapted to specific questions about HR in mammalian cells. The effect of substrate structures (heterologies, insertions/deletions, GT repeats, transcription) and consequences of DNA double strand breaks induced by ionizing radiation or endonuclease (especially the rare-cutting endonuclease ISce-I) on HR are discussed. Finally, transgenic mouse models using tandem repeats are briefly presented.
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Affiliation(s)
- S Lambert
- UMR 217 CNRS, CEA, DSV, DRR, Fontenay aux Roses, France
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Wahls WP. Meiotic recombination hotspots: shaping the genome and insights into hypervariable minisatellite DNA change. Curr Top Dev Biol 1998; 37:37-75. [PMID: 9352183 PMCID: PMC3151733 DOI: 10.1016/s0070-2153(08)60171-4] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Meiotic homologous recombination serves three principal roles. First, recombination reassorts the linkages between newly-arising alleles to provide genetic diversity upon which natural selection can act. Second, recombination is used to repair certain types of DNA damage to provide a mechanism of genomic homeostasis. Third, with few exceptions homologous recombination is required for the appropriate segregation of homologous chromosomes during meiosis. Recombination rates are elevated near DNA sites called "recombination hotspots." These sites influence the distribution of recombination along chromosomes and the timing of recombination during the life cycle. Recent advances have revealed biochemical steps of hotspot activation and have suggested that hotspots may regulate when and where recombination occurs. Two models for hotspot activation, one in which hotspots act early in the recombination pathway and one in which hotspots act late in the recombination pathway, are presented. The latter model can account for changes at hypervariable minisatellite DNA in metazoan genomes by invoking resolution of Holliday junctions at minisatellite DNA repeats.
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Affiliation(s)
- Wayne P. Wahls
- Department of Biochemistry, Vanderbilt University School of Medicine, 621 Light Hall, Nashville, TN 37232-0146, (615) 322-3063 voice; (615) 343-0704 fax
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Wahls WP, Moore PD. Recombination hotspot activity of hypervariable minisatellite DNA requires minisatellite DNA binding proteins. SOMATIC CELL AND MOLECULAR GENETICS 1998; 24:41-51. [PMID: 9776980 PMCID: PMC3151739 DOI: 10.1007/bf02677494] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Hypervariable minisatellite DNA repeats are found at tens of thousands of loci in the mammalian genome. These sequences stimulate homologous recombination in mammalian cells [Cell 60:95-103]. To test the hypothesis that protein-DNA interaction is required for hotspot function in vivo, we determined whether a second protein binding nearby could abolish hotspot activity. Intermolecular recombination between pairs of plasmid substrates was measured in the presence or absence of the cis-acting recombination hotspot and in the presence or absence of the second trans-acting DNA binding protein. Minisatellite DNA had hotspot activity in two cell lines, but lacked hotspot activity in two closely related cell lines expressing a site-specific helicase that bound to DNA adjacent to the hotspot. Suppression of hotspot function occurred for both replicating and non-replicating recombination substrates. These results indicate that hotspot activity in vivo requires site occupancy by minisatellite DNA binding proteins.
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Affiliation(s)
- W P Wahls
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA
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Abstract
The effect of GT/CA dinucleotide repeat tracts on RecA-dependent homologous recombination was examined in vitro. By measuring the binding of RecA protein to oligonucleotides containing GT or CA repeats using the surface plasmon resonance (BIAcore), we show that the efficiency of RecA protein binding is sequence dependent: the protein binds to non-repetitive, poly(CA) or poly(GT) sequences with an increasing affinity. This preferential binding to repetitive sequences is specific for RecA protein and is not observed with the single-strand DNA binding (SSB) protein. Despite the fact that RecA filaments formed on GT tracts efficiently bind duplex DNAs, they are unable to promote stable joint formation. Moreover, strand exchange between a duplex DNA and a fully homologous single-stranded DNA (ssDNA) containing dinucleotide repeats, is inhibited as a function of the length of the repetitive tract. The number of molecules which underwent a complete strand exchange decreased from 100% to 80% and 30% for DNA containing seven, 16 and 39 GT repeats, respectively. The inhibition is less pronounced when the ssDNA contains CA instead of GT dinucleotide repeats. We propose that the high affinity of RecA protein for (CA)n or (GT)n tracts prevents strand exchange from progressing across such sequences. Thus, our results suggest that repetitive tracts of dinucleotides CA/GT could influence recombinational activity potentially leading to an increase in genomic rearrangements.
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Affiliation(s)
- M Dutreix
- Institut Curie, section de Recherche UMR144-CNRS, Paris, France
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Heikkinen J, Toppinen T, Yeowell H, Krieg T, Steinmann B, Kivirikko KI, Myllylä R. Duplication of seven exons in the lysyl hydroxylase gene is associated with longer forms of a repetitive sequence within the gene and is a common cause for the type VI variant of Ehlers-Danlos syndrome. Am J Hum Genet 1997; 60:48-56. [PMID: 8981946 PMCID: PMC1712545] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The type VI variant of the Ehlers-Danlos syndrome (EDS) is a recessively inherited connective tissue disorder which, in most families, is due to a deficiency in lysyl hydroxylase activity. We have recently characterized a homozygous duplication of 8.9 kb in the lysyl hydroxylase gene (PLOD) in two EDS VI families. The duplication is caused by a homologous recombination of Alu sequences in introns 9 and 16. Using PCR, we have analyzed 26 additional EDS VI families from various countries and found that 7 of them have this duplication. Our data has shown a frequency of 19.1% for this mutant allele among 35 EDS VI families studied by us so far. Our haplotype analysis shows a variation in the sequence of DNA region surrounding the duplication. There is an association between a particular allele size class, the long form, at the dinucleotide repeat within intron 16 and the duplication mutation in PLOD. Screening of a general population revealed one positive finding among 582 alleles tested. An abnormal sequence in exon 17 of the gene, which generated a stop codon in the exon sequence and aberrant mRNA processing, was responsible for the nonfunctionality of the other allele in one of the compound heterozygous patients.
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Affiliation(s)
- J Heikkinen
- Biocenter and Department of Biochemistry, University of Oulu, Finland
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Wiesmüller L, Cammenga J, Deppert WW. In vivo assay of p53 function in homologous recombination between simian virus 40 chromosomes. J Virol 1996; 70:737-44. [PMID: 8551610 PMCID: PMC189874 DOI: 10.1128/jvi.70.2.737-744.1996] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
To investigate a possible role of p53 in DNA exchange mechanisms, we have developed a model system which allows us to quantify homologous recombination rates in eukaryotic cells. We generated two types of simian virus 40 (SV40) whose genomes were mutated in such a way that upon double infection of monkey cells, virus particles can be released only after interchromosomal exchange of genetic material. This test system allowed us to determine recombination rates in the order of 10(-4) to 10(-6) for chromatin-associated SV40 genomes. To study the role of p53-T-antigen (T-Ag) complexes in this process, we designed viral test genomes with an additional mutation leading to a single amino acid exchange in T-Ag (D402H) and specifically blocking T-Ag-p53 interactions. Analysis of primary rhesus monkey cells endogenously expressing wild-type p53 showed a decreased recombination rate upon loss of efficient T-Ag-p53 complex formation. However, cells expressing mutant p53 (LLC-MK2 cells), the introduction of mutant T-Ag did not affect the DNA exchange rates. Our data are interpreted to indicate an inhibitory role of wild-type p53 in recombination. In agreement with this hypothesis, p53-T-Ag complex formation alleviates the inhibitory effect of wild-type p53.
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Affiliation(s)
- L Wiesmüller
- Heinrich-Pette-Institut für Experimentelle Virologie und Immunologie an der Universität Hamburg, Germany
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Zhang Q, Wrana JL, Sodek J. Characterization of the promoter region of the porcine opn (osteopontin, secreted phosphoprotein 1) gene. Identification of positive and negative regulatory elements and a 'silent' second promoter. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 207:649-59. [PMID: 1633816 DOI: 10.1111/j.1432-1033.1992.tb17092.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Osteopontin (secreted phosphoprotein-1, Opn) is a phosphorylated glycoprotein expressed by transformed cells, macrophages, activated T-lymphocytes, specialized epithelial cells and bone cells that is characteristically enriched in milk and in the mineralized matrix of bone. The synthesis of Opn by bone cells is regulated by glucocorticoids and growth factors, which promote bone formation, and by the osteotropic hormone calcitriol (1,25-dihydroxycholecalciferol) and retinoic acid, which mediate bone resorption, indicating a bifunctional role for this protein in bone remodelling. To study the transcriptional regulation of the opn gene, two genomic clones (10 and 15 kb) encoding the opn gene were isolated from a porcine liver genomic library cloned into lambda phage. From the 15-kb clone a 4-kb EcoRI fragment containing the first two exons and 2.6 kb of the 5' flanking region of the opn gene was sequenced, and the transcriptional start site determined by primer extension analysis and S1 nuclease mapping. To identify the opn promoter, chimeric chloramphenicol acetyltransferase constructs were prepared using fragments from the first intron and the 5' flanking region of the opn gene. Transient transfection of porcine bone cells with these constructs showed strong promoter activity located within 74 bp upstream from the transcription initiation site. Within this region a TATA sequence, TTTAAA, was identified at positions -26 to -31. However, the highest transcription rate was observed in a construct extending 180 bp upstream that included a CCGCCC Sp1 binding sequence (-63 to -68), and an AP1 site (-74 to -80). Further upstream in the 5' flanking region and within the first intron of the opn, a number of consensus sequences could be identified. Chimeric constructs containing a GGGTCAtatGGTTCA direct repeat consensus sequence for a vitamin D3 response element located at nucleotides -2245 to -2259 responded to the addition of 0.1 microM calcitriol by a 2.5-fold stimulation of transcription, although a greater than 2-fold increase was also observed in shorter constructs -180 to -905 lacking such a consensus sequence. Promoter activity was also exhibited by a region containing a TTTAAA sequence in the first intron that corresponded to the putative promoter site reported for mouse opn in macrophages (Miyazaki, Y., Setoguchi, M., Yoshida, S., Higuchi, Y., Akizuki, S. & Yamamoto, S. (1990) J. Biol. Chem. 265, 14432-14438).(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- Q Zhang
- MRC Group in Periodontal Physiology, University of Toronto, Canada
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Satyanarayana K, Strominger JL. DNA sequences near a meiotic recombinational breakpoint within the human HLA-DQ region. Immunogenetics 1992; 35:235-40. [PMID: 1541483 DOI: 10.1007/bf00166828] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The molecular organization of HLA-DQ regions derived from DR7, DQw2, and DR4, DQw3 parental haplotypes and DR7, DQw3, a presumed recombinant haplotype, have been studied to define the sequences between DQA1 and DQB1 which may have been involved in this recombinational event. The breakpoint was localized in the intergenic region near the 3' end of the DQB1 gene by restriction mapping. DNA sequences in the immediate vicinity of the breakpoint in DR7, DQw2 (parental), and DR7, DQw3 (recombinant) haplotypes revealed the presence of (CA)22 repeats, minisatellite-related sequences and GC-rich sequences. The intergenic regions varied considerably depending on the haplotype and contained several additional types of repetitive sequences including Alu and LINE repeats. Some of these sequences are related to sequences previously suggested to be involved in meiotic or somatic recombination. In particular, (CA)n repeats, which can adopt the Z-DNA conformation, have previously been shown to promote recombination in several systems.
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Affiliation(s)
- K Satyanarayana
- Department of Biochemistry and Molecular Biology, Harvard University, Cambridge, MA 02138
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Affiliation(s)
- A A Morley
- Department of Haematology, Flinders Medical Centre, Bedford Park, South Australia
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Mucenski ML, McLain K, Kier AB, Swerdlow SH, Schreiner CM, Miller TA, Pietryga DW, Scott WJ, Potter SS. A functional c-myb gene is required for normal murine fetal hepatic hematopoiesis. Cell 1991; 65:677-89. [PMID: 1709592 DOI: 10.1016/0092-8674(91)90099-k] [Citation(s) in RCA: 819] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The c-myb proto-oncogene encodes a sequence-specific DNA-binding protein. To better understand its normal biological function, we have altered the c-myb gene by homologous recombination in mouse embryonic stem cells. Resulting homozygous c-myb mutant mice displayed an interesting phenotype. At day 13 of gestation these mice appeared normal, suggesting that c-myb is not essential for early development. By day 15, however, the mutant mice were severely anemic. Analysis indicated that embryonic erythropoiesis, which occurs in the yolk sac, was not impaired by the c-myb alteration. Adult-type erythropoiesis, which first takes place in the fetal liver, was greatly diminished in c-myb mutants, however. Additional hematopoietic lineages were similarly affected. These results are compatible with a role for c-myb in maintaining the proliferative state of hematopoietic progenitor cells.
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Affiliation(s)
- M L Mucenski
- Children's Hospital Research Foundation, Department of Pediatrics, Cincinnati, Ohio
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