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Glaser S, Lubitz S, Loveland KL, Ohbo K, Robb L, Schwenk F, Seibler J, Roellig D, Kranz A, Anastassiadis K, Stewart AF. The histone 3 lysine 4 methyltransferase, Mll2, is only required briefly in development and spermatogenesis. Epigenetics Chromatin 2009; 2:5. [PMID: 19348672 PMCID: PMC2674429 DOI: 10.1186/1756-8935-2-5] [Citation(s) in RCA: 133] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2008] [Accepted: 04/06/2009] [Indexed: 12/18/2022] Open
Abstract
Background Histone methylation is thought to be central to the epigenetic mechanisms that maintain and confine cellular identity in multi-cellular organisms. To examine epigenetic roles in cellular homeostasis, we conditionally mutated the histone 3 lysine 4 methyltransferase, Mll2, in embryonic stem (ES) cells, during development and in adult mice using tamoxifen-induced Cre recombination. Results In ES cells, expression profiling unexpectedly revealed that only one gene, Magoh2, is dependent upon Mll2 and few other genes were affected. Loss of Mll2 caused loss of H3K4me3 at the Magoh2 promoter and concomitant gain of H3K27me3 and DNA methylation. Hence Mll2, which is orthologous to Drosophila Trithorax, is required to prevent Polycomb-Group repression of the Magoh2 promoter, and repression is further accompanied by DNA methylation. Early loss of Mll2 in utero recapitulated the embryonic lethality found in Mll2-/- embryos. However, loss of Mll2 after E11.5 produced mice without notable pathologies. Hence Mll2 is not required for late development, stem cells or homeostasis in somatic cell types. However it is required in the germ cell lineage. Spermatogenesis was lost upon removal of Mll2, although spermatogonia A persisted. Conclusion These data suggest a bimodal recruit and maintain model whereby Mll2 is required to establish certain epigenetic decisions during differentiation, which are then maintained by redundant mechanisms. We also suggest that these mechanisms relate to the epigenetic maintenance of CpG island promoters.
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Ding L, Paszkowski-Rogacz M, Nitzsche A, Slabicki MM, Heninger AK, de Vries I, Kittler R, Junqueira M, Shevchenko A, Schulz H, Hubner N, Doss MX, Sachinidis A, Hescheler J, Iacone R, Anastassiadis K, Stewart AF, Pisabarro MT, Caldarelli A, Poser I, Theis M, Buchholz F. A genome-scale RNAi screen for Oct4 modulators defines a role of the Paf1 complex for embryonic stem cell identity. Cell Stem Cell 2009; 4:403-15. [PMID: 19345177 DOI: 10.1016/j.stem.2009.03.009] [Citation(s) in RCA: 218] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2008] [Revised: 02/12/2009] [Accepted: 03/16/2009] [Indexed: 11/29/2022]
Abstract
Pluripotent embryonic stem cells (ESCs) maintain self-renewal while ensuring a rapid response to differentiation cues. The identification of genes maintaining ESC identity is important to develop these cells for their potential therapeutic use. Here we report a genome-scale RNAi screen for a global survey of genes affecting ESC identity via alteration of Oct4 expression. Factors with the strongest effect on Oct4 expression included components of the Paf1 complex, a protein complex associated with RNA polymerase II. Using a combination of proteomics, expression profiling, and chromatin immunoprecipitation, we demonstrate that the Paf1C binds to promoters of key pluripotency genes, where it is required to maintain a transcriptionally active chromatin structure. The Paf1C is developmentally regulated and blocks ESC differentiation upon overexpression, and the knockdown in ESCs causes expression changes similar to Oct4 or Nanog depletions. We propose that the Paf1C plays an important role in maintaining ESC identity.
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78
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Shaw PE, Stewart AF. Identification of protein/DNA contacts with dimethyl sulfate: methylation protection and methylation interference. Methods Mol Biol 2009; 543:97-104. [PMID: 19378162 DOI: 10.1007/978-1-60327-015-1_8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Sequence-specific protein/DNA contacts direct most transcription factors to binding sites within the promoters of genes they regulate. Several chemical probes, such as dimethyl sulfate, have been used to obtain information on these sites of interaction. Protection and interference patterns frequently correspond to highly conserved positions within binding sites and are often specific for a given transcription factor or family of factors. The methods described here can be used to identify sites within a DNA sequence that are bound by nuclear factors or to characterise the contacts made by a purified factor or recombinant protein in vitro. As methylation protection is the in vitro equivalent of in vivo genomic footprinting, a direct comparison between in vivo and in vitro footprints can be made.
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Fu J, Wenzel SC, Perlova O, Wang J, Gross F, Tang Z, Yin Y, Stewart AF, Müller R, Zhang Y. Efficient transfer of two large secondary metabolite pathway gene clusters into heterologous hosts by transposition. Nucleic Acids Res 2008; 36:e113. [PMID: 18701643 PMCID: PMC2553598 DOI: 10.1093/nar/gkn499] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Horizontal gene transfer by transposition has been widely used for transgenesis in prokaryotes. However, conjugation has been preferred for transfer of large transgenes, despite greater restrictions of host range. We examine the possibility that transposons can be used to deliver large transgenes to heterologous hosts. This possibility is particularly relevant to the expression of large secondary metabolite gene clusters in various heterologous hosts. Recently, we showed that the engineering of large gene clusters like type I polyketide/nonribosomal peptide pathways for heterologous expression is no longer a bottleneck. Here, we apply recombineering to engineer either the epothilone (epo) or myxochromide S (mchS) gene cluster for transpositional delivery and expression in heterologous hosts. The 58-kb epo gene cluster was fully reconstituted from two clones by stitching. Then, the epo promoter was exchanged for a promoter active in the heterologous host, followed by engineering into the MycoMar transposon. A similar process was applied to the mchS gene cluster. The engineered gene clusters were transferred and expressed in the heterologous hosts Myxococcus xanthus and Pseudomonas putida. We achieved the largest transposition yet reported for any system and suggest that delivery by transposon will become the method of choice for delivery of large transgenes, particularly not only for metabolic engineering but also for general transgenesis in prokaryotes and eukaryotes.
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80
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Poser I, Sarov M, Hutchins JRA, Hériché JK, Toyoda Y, Pozniakovsky A, Weigl D, Nitzsche A, Hegemann B, Bird AW, Pelletier L, Kittler R, Hua S, Naumann R, Augsburg M, Sykora MM, Hofemeister H, Zhang Y, Nasmyth K, White KP, Dietzel S, Mechtler K, Durbin R, Stewart AF, Peters JM, Buchholz F, Hyman AA. Erratum: Corrigendum: BAC TransgeneOmics: a high-throughput method for exploration of protein function in mammals. Nat Methods 2008. [DOI: 10.1038/nmeth0808-748b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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81
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Poser I, Sarov M, Hutchins JRA, Hériché JK, Toyoda Y, Pozniakovsky A, Weigl D, Nitzsche A, Hegemann B, Bird AW, Pelletier L, Kittler R, Hua S, Naumann R, Augsburg M, Sykora MM, Hofemeister H, Zhang Y, Nasmyth K, White KP, Dietzel S, Mechtler K, Durbin R, Stewart AF, Peters JM, Buchholz F, Hyman AA. BAC TransgeneOmics: a high-throughput method for exploration of protein function in mammals. Nat Methods 2008; 5:409-15. [PMID: 18391959 PMCID: PMC2871289 DOI: 10.1038/nmeth.1199] [Citation(s) in RCA: 488] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2008] [Accepted: 03/17/2008] [Indexed: 12/11/2022]
Abstract
The interpretation of genome sequences requires reliable and standardized methods to assess protein function at high throughput. Here we describe a fast and reliable pipeline to study protein function in mammalian cells based on protein tagging in bacterial artificial chromosomes (BACs). The large size of the BAC transgenes ensures the presence of most, if not all, regulatory elements and results in expression that closely matches that of the endogenous gene. We show that BAC transgenes can be rapidly and reliably generated using 96-well-format recombineering. After stable transfection of these transgenes into human tissue culture cells or mouse embryonic stem cells, the localization, protein-protein and/or protein-DNA interactions of the tagged protein are studied using generic, tag-based assays. The same high-throughput approach will be generally applicable to other model systems.
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82
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Vintersten K, Testa G, Naumann R, Anastassiadis K, Stewart AF. Bacterial artificial chromosome transgenesis through pronuclear injection of fertilized mouse oocytes. Methods Mol Biol 2008; 415:83-100. [PMID: 18370149 DOI: 10.1007/978-1-59745-570-1_5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
In the mouse, conventional transgenes often produced unpredictable results mainly because they were too small to recapitulate a natural gene context. Bacterial artificial chromosomes (BACs) are large enough to encompass the natural context of most mammalian genes and consequently deliver more reliable recapitulations of their endogenous counterparts. Furthermore, recombineering methods now make it easy to engineer precise changes in a BAC transgene. Consequently, BACs have become the preferred vehicle for mouse transgenesis. Here, we detail methods for BAC transgenesis through pronuclear injection of fertilized oocytes.
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83
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Augui S, Filion GJ, Huart S, Nora E, Guggiari M, Maresca M, Stewart AF, Heard E. Sensing X chromosome pairs before X inactivation via a novel X-pairing region of the Xic. Science 2007; 318:1632-6. [PMID: 18063799 DOI: 10.1126/science.1149420] [Citation(s) in RCA: 158] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Mammalian dosage compensation involves silencing of one of the two X chromosomes in females and is controlled by the X-inactivation center (Xic). The Xic, which includes Xist and its antisense transcription unit Tsix/Xite, somehow senses the number of X chromosomes and triggers Xist up-regulation from one of the two X chromosomes in females. We found that a segment of the mouse Xic lying several hundred kilobases upstream of Xist brings the two Xics together before the onset of X inactivation. This region can autonomously drive Xic trans-interactions even as an ectopic single-copy transgene. Its introduction into male embryonic stem cells is strongly selected against, consistent with a possible role in trans-activating Xist. We propose that homologous associations driven by this novel X-pairing region (Xpr) of the Xic enable a cell to sense that more than one X chromosome is present and coordinate reciprocal Xist/Tsix expression.
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84
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Gross F, Ring MW, Perlova O, Fu J, Schneider S, Gerth K, Kuhlmann S, Stewart AF, Zhang Y, Müller R. Metabolic engineering of Pseudomonas putida for methylmalonyl-CoA biosynthesis to enable complex heterologous secondary metabolite formation. ACTA ACUST UNITED AC 2007; 13:1253-64. [PMID: 17185221 DOI: 10.1016/j.chembiol.2006.09.014] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2006] [Revised: 09/06/2006] [Accepted: 09/28/2006] [Indexed: 11/30/2022]
Abstract
An operon consisting of three open reading frames, annotated in silico as methylmalonyl-CoA (mm-CoA) epimerase, mm-CoA mutase (MCM), and meaB, was identified in the sequencing project of the myxobacterium Sorangium cellulosum So ce56. This putative MCM pathway operon was subcloned from a bacterial artificial chromosome by Red/ET recombineering onto a minimal replicon derived from p15A. This plasmid was modified for integration and heterologous expression in Pseudomonas putida to enable the production of complex secondary metabolites requiring mm-CoA as precursor. Methylmalonate was identified in the recombinant P. putida strain by an analysis method based on gas chromatography/mass spectrometry. The engineered strain is able to synthesize polyketides requiring mm-CoA as an extender unit, which was demonstrated by the production of myxothiazol after integration of the biosynthetic gene cluster into the chromosome, followed by induction of expression.
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85
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Lubitz S, Glaser S, Schaft J, Stewart AF, Anastassiadis K. Increased apoptosis and skewed differentiation in mouse embryonic stem cells lacking the histone methyltransferase Mll2. Mol Biol Cell 2007; 18:2356-66. [PMID: 17429066 PMCID: PMC1877088 DOI: 10.1091/mbc.e06-11-1060] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Epigenetic regulation by histone methyltransferases provides transcriptional memory and inheritable propagation of gene expression patterns. Potentially, the transition from a pluripotent state to lineage commitment also includes epigenetic instructions. The histone 3 lysine 4 methyltransferase Mll2/Wbp7 is essential for embryonic development. Here, we used embryonic stem (ES) cell lines deficient for Mll2 to examine its function more accurately. Mll2-/- ES cells are viable and retain pluripotency, but they display cell proliferation defects due to an enhanced rate of apoptosis. Apoptosis was not relieved by caspase inhibition and correlated with decreased Bcl2 expression. Concordantly, Mll2 binds to the Bcl2 gene and H3K4me(3) levels are reduced at the binding site when Mll2 is absent. In vitro differentiation showed delays along representative pathways for all three germ layers. Although ectodermal delays were severe and mesodermal delays persisted at about three days, endodermal differentiation seemed to recover and overshoot, concomitant with prolonged Oct4 gene expression. Hence, Mll2 is not required for ES cell self-renewal or the complex changes in gene expression involved in lineage commitment, but it contributes to the coordination and timing of early differentiation decisions.
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86
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Erler A, Maresca M, Fu J, Stewart AF. Recombineering reagents for improved inducible expression and selection marker re-use in Schizosaccharomyces pombe. Yeast 2006; 23:813-23. [PMID: 16921581 DOI: 10.1002/yea.1396] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The fission yeast Schizosaccharomyces pombe is an excellent model organism for cell biology. However, its genetic toolbox is less developed than that of Saccharomyces cerevisiae. In the first part of this study we describe an improved inducible expression vector based on tetracycline regulation of the CaMV35S promoter, which is also capable of chromosomal integration and therefore works in minimal and in rich media. We found that anhydrotetracycline is a superior ligand for induction. Maximum expression levels were observed after 12 h in minimal media (EMM) and after 9 h in rich media (YES), which is faster than the nmt1 promoter system. The system was combined with a convenient recombineering-based subcloning strategy for ease of cloning. In the second part we present four template plasmids, pSVEM-bsd, pSVEM-nat, pSVEM-kan and pSVEM-hph, which harbour four recyclable disruption cassettes based on the Cre recombinase lox71/66 strategy for use in PCR targeting methods. Cre-mediated excision leaves a non-functional mutant lox site in the genome, allowing the reiterative usage of these cassettes for multiple targetings. These cassettes are also configured with dual eukaryotic/prokaryotic promoters so that they can be used for recombineering in E. coli. Amongst other purposes, this permits the rapid and convenient creation of targeting constructs with much longer homology arms for difficult and complex targetings in the Sz. pombe genome.
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87
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Sarov M, Schneider S, Pozniakovski A, Roguev A, Ernst S, Zhang Y, Hyman AA, Stewart AF. A recombineering pipeline for functional genomics applied to Caenorhabditis elegans. Nat Methods 2006; 3:839-44. [PMID: 16990816 DOI: 10.1038/nmeth933] [Citation(s) in RCA: 157] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2006] [Accepted: 08/07/2006] [Indexed: 12/28/2022]
Abstract
We present a new concept in DNA engineering based on a pipeline of serial recombineering steps in liquid culture. This approach is fast, straightforward and facilitates simultaneous processing of multiple samples in parallel. We validated the approach by generating green fluorescent protein (GFP)-tagged transgenes from Caenorhabditis briggsae genomic clones in a multistep pipeline that takes only 4 d. The transgenes were engineered with minimal disturbance to the natural genomic context so that the correct level and pattern of expression will be secured after transgenesis. An example transgene for the C. briggsae ortholog of lin-59 was used for ballistic transformation in Caenorhabditis elegans. We show that the cross-species transgene is correctly expressed and rescues RNA interference (RNAi)-mediated knockdown of the endogenous C. elegans gene. The strategy that we describe adapts the power of recombineering in Escherichia coli for fluent DNA engineering to a format that can be directly scaled up for genomic projects.
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88
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Dehé PM, Dichtl B, Schaft D, Roguev A, Pamblanco M, Lebrun R, Rodríguez-Gil A, Mkandawire M, Landsberg K, Shevchenko A, Shevchenko A, Rosaleny LE, Tordera V, Chávez S, Stewart AF, Géli V. Protein Interactions within the Set1 Complex and Their Roles in the Regulation of Histone 3 Lysine 4 Methylation. J Biol Chem 2006; 281:35404-12. [PMID: 16921172 DOI: 10.1074/jbc.m603099200] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Set1 is the catalytic subunit and the central component of the evolutionarily conserved Set1 complex (Set1C) that methylates histone 3 lysine 4 (H3K4). Here we have determined protein/protein interactions within the complex and related the substructure to function. The loss of individual Set1C subunits differentially affects Set1 stability, complex integrity, global H3K4 methylation, and distribution of H3K4 methylation along active genes. The complex requires Set1, Swd1, and Swd3 for integrity, and Set1 amount is greatly reduced in the absence of the Swd1-Swd3 heterodimer. Bre2 and Sdc1 also form a heteromeric subunit, which requires the SET domain for interaction with the complex, and Sdc1 strongly interacts with itself. Inactivation of either Bre2 or Sdc1 has very similar effects. Neither is required for complex integrity, and their removal results in an increase of H3K4 mono- and dimethylation and a severe decrease of trimethylation at the 5' end of active coding regions but a decrease of H3K4 dimethylation at the 3' end of coding regions. Cells lacking Spp1 have a reduced amount of Set1 and retain a fraction of trimethylated H3K4, whereas cells lacking Shg1 show slightly elevated levels of both di- and trimethylation. Set1C associates with both serine 5- and serine 2-phosphorylated forms of polymerase II, indicating that the association persists to the 3' end of transcribed genes. Taken together, our results suggest that Set1C subunits stimulate Set1 catalytic activity all along active genes.
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89
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Perlova O, Fu J, Kuhlmann S, Krug D, Stewart AF, Zhang Y, Müller R. Reconstitution of the myxothiazol biosynthetic gene cluster by Red/ET recombination and heterologous expression in Myxococcus xanthus. Appl Environ Microbiol 2006; 72:7485-94. [PMID: 16997979 PMCID: PMC1694261 DOI: 10.1128/aem.01503-06] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although many secondary metabolites exhibiting important pharmaceutical and agrochemical activities have been isolated from myxobacteria, most of these microorganisms remain difficult to handle genetically. To utilize their metabolic potential, heterologous expression methodologies are currently being developed. Here, the Red/ET recombination technology was used to perform all required gene cluster engineering steps in Escherichia coli prior to the transfer into the chromosome of the heterologous host. We describe the integration of the complete 57-kbp myxothiazol biosynthetic gene cluster reconstituted from two cosmids from a cosmid library of the myxobacterium Stigmatella aurantiaca DW4-3/1 into the chromosome of the thus far best-characterized myxobacterium, Myxococcus xanthus, in one step. The successful integration and expression of the myxothiazol biosynthetic genes in M. xanthus results in the production of myxothiazol in yields comparable to the natural producer strain.
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90
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Wang J, Sarov M, Rientjes J, Fu J, Hollak H, Kranz H, Xie W, Stewart AF, Zhang Y. An improved recombineering approach by adding RecA to lambda Red recombination. Mol Biotechnol 2006; 32:43-53. [PMID: 16382181 DOI: 10.1385/mb:32:1:043] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Recombineering is the use of homologous recombination in Escherichia coli for DNA engineering. Of several approaches, use of the lambda phage Red operon is emerging as the most reliable and flexible. The Red operon includes three components: Redalpha, a 5' to 3' exonuclease, Redbeta, an annealing protein, and Redgamma, an inhibitor of the major E. coli exonuclease and recombination complex, RecBCD. Most E. coli cloning hosts are recA deficient to eliminate recombination and therefore enhance the stability of cloned DNAs. However, loss of RecA also impairs general cellular integrity. Here we report that transient RecA co-expression enhances the total number of successful recombinations in bacterial artificial chromosomes (BACs), mostly because the E. coli host is more able to survive the stresses of DNA transformation procedures. We combined this practical improvement with the advantages of a temperature-sensitive version of the low copy pSC101 plasmid to develop a protocol that is convenient and more efficient than any recombineering procedure, for use of either double- or single-stranded DNA, published to date.
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91
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Glaser S, Schaft J, Lubitz S, Vintersten K, van der Hoeven F, Tufteland KR, Aasland R, Anastassiadis K, Ang SL, Stewart AF. Multiple epigenetic maintenance factors implicated by the loss of Mll2 in mouse development. Development 2006; 133:1423-32. [PMID: 16540515 DOI: 10.1242/dev.02302] [Citation(s) in RCA: 209] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Epigenesis is the process whereby the daughters of a dividing cell retain a chromatin state determined before cell division. The best-studied cases involve the inheritance of heterochromatic chromosomal domains, and little is known about specific gene regulation by epigenetic mechanisms. Recent evidence shows that epigenesis pivots on methylation of nucleosomes at histone 3 lysines 4, 9 or 27. Bioinformatics indicates that mammals have several enzymes for each of these methylations, including at least six histone 3 lysine 4 methyltransferases. To look for evidence of gene-specific epigenetic regulation in mammalian development, we examined one of these six, Mll2, using a multipurpose allele in the mouse to ascertain the loss-of-function phenotype. Loss of Mll2 slowed growth, increased apoptosis and retarded development, leading to embryonic failure before E11.5. Using chimera experiments, we demonstrated that Mll2 is cell-autonomously required. Evidence for gene-specific regulation was also observed. Although Mox1 and Hoxb1 expression patterns were correctly established, they were not maintained in the absence of Mll2, whereas Wnt1 and Otx2were. The Mll2 loss-of-function phenotype is different from that of its sister gene Mll, and they regulate different Hox complex genes during ES cell differentiation. Therefore, these two closely related epigenetic factors play different roles in development and maintain distinct gene expression patterns. This suggests that other epigenetic factors also regulate particular patterns and that development entails networks of epigenetic specificities.
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Abstract
The mouse is the foremost vertebrate experimental model because its genome can be precisely and variously engineered. Now that the mouse genome has been sequenced and annotated, the task of mutating each gene is feasible, and an international cooperation is providing mutated embryonic stem cells and mice as readily available resources. Because these resources will change biomedical research, decisions about their nature will have far-reaching effects. It is therefore timely to consider topical issues for mouse genome engineering, such as the background genotype; homologous, site-specific and transpositional recombination; conditional mutagenesis; RNA-mediated interference; and functional genomics with embryonic stem cells.
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93
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Schnütgen F, Stewart AF, von Melchner H, Anastassiadis K. Engineering embryonic stem cells with recombinase systems. Methods Enzymol 2006; 420:100-36. [PMID: 17161696 DOI: 10.1016/s0076-6879(06)20007-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The combined use of site-specific recombination and gene targeting or trapping in embryonic stem cells (ESCs) has resulted in the emergence of technologies that enable the induction of mouse mutations in a prespecified temporal and spatially restricted manner. Their large-scale implementation by several international mouse mutagenesis programs will lead to the assembly of a library of ES cell lines harboring conditional mutations in every single gene of the mouse genome. In anticipation of this unprecedented resource, this chapter will focus on site-specific recombination strategies and issues pertinent to ESCs and mice. The upcoming ESC resource and the increasing sophistication of site-specific recombination technologies will greatly assist the functional annotation of the human genome and the animal modeling of human disease.
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94
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Sarov M, Stewart AF. The best control for the specificity of RNAi. Trends Biotechnol 2005; 23:446-8. [PMID: 15979179 DOI: 10.1016/j.tibtech.2005.06.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2005] [Revised: 04/08/2005] [Accepted: 06/10/2005] [Indexed: 11/17/2022]
Abstract
RNA interference (RNAi) is revolutionizing functional genomics. However, there are several reasons to be concerned about the specificity and off-target effects of this technique. A recent paper by Kittler et al. describes a straightforward way to validate RNAi specificity, which exploits the increasing availability of bacterial artificial chromosome (BAC) clone resources. Genetic rescue of the RNAi phenotype by BAC transgenesis is the best control yet described for specificity, and has further implications for reverse genetics.
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95
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Zhang DJ, Wang Q, Wei J, Baimukanova G, Buchholz F, Stewart AF, Mao X, Killeen N. Selective expression of the Cre recombinase in late-stage thymocytes using the distal promoter of the Lck gene. THE JOURNAL OF IMMUNOLOGY 2005; 174:6725-31. [PMID: 15905512 DOI: 10.4049/jimmunol.174.11.6725] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Transgenic mouse lines were generated that express the Cre recombinase under the control of the distal promoter of the mouse Lck gene. Cre recombination in four of these lines of transgenic mice was characterized at the single cell level using ROSA26-regulated loxP-Stop-loxP-betageo and loxP-Stop-loxP-YFP reporter mouse lines. Two of the lines showed T cell-restricted Cre recombination, whereas the other two also expressed Cre in B cells, NK cells, and monocytes. Cre recombination began at a late stage of T cell development (at or after up-regulation of the TCR during positive selection) in the two T cell-restricted lines. Lines of mice that express the Cre recombinase at late stages of thymocyte development are of value for determining the impact of mutations on T cell function in the absence of complicating effects on early thymocyte selection.
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96
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Nedelcheva MN, Roguev A, Dolapchiev LB, Shevchenko A, Taskov HB, Shevchenko A, Stewart AF, Stoynov SS. Uncoupling of unwinding from DNA synthesis implies regulation of MCM helicase by Tof1/Mrc1/Csm3 checkpoint complex. J Mol Biol 2005; 347:509-21. [PMID: 15755447 DOI: 10.1016/j.jmb.2005.01.041] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2004] [Revised: 01/11/2005] [Accepted: 01/13/2005] [Indexed: 10/25/2022]
Abstract
The replicative DNA helicases can unwind DNA in the absence of polymerase activity in vitro. In contrast, replicative unwinding is coupled with DNA synthesis in vivo. The temperature-sensitive yeast polymerase alpha/primase mutants cdc17-1, pri2-1 and pri1-m4, which fail to execute the early step of DNA replication, have been used to investigate the interaction between replicative unwinding and DNA synthesis in vivo. We report that some of the plasmid molecules in these mutant strains became extensively negatively supercoiled when DNA synthesis is prevented. In contrast, additional negative supercoiling was not detected during formation of DNA initiation complex or hydroxyurea replication fork arrest. Together, these results indicate that the extensive negative supercoiling of DNA is a result of replicative unwinding, which is not followed by DNA synthesis. The limited number of unwound plasmid molecules and synthetic lethality of polymerase alpha or primase with checkpoint mutants suggest a checkpoint regulation of the replicative unwinding. In concordance with this suggestion, we found that the Tof1/Csm3/Mrc1 checkpoint complex interacts directly with the MCM helicase during both replication fork progression and when the replication fork is stalled.
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Wenzel SC, Gross F, Zhang Y, Fu J, Stewart AF, Müller R. Heterologous expression of a myxobacterial natural products assembly line in pseudomonads via red/ET recombineering. CHEMISTRY & BIOLOGY 2005; 12:349-56. [PMID: 15797219 DOI: 10.1016/j.chembiol.2004.12.012] [Citation(s) in RCA: 148] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2004] [Revised: 12/20/2004] [Accepted: 12/21/2004] [Indexed: 11/17/2022]
Abstract
Natural products of microbial origin are widely used as pharmaceuticals and in agrochemistry. These compounds are often biosynthesized by multifunctional megasynthetases whose genetic engineering and heterologous expression offer considerable promise, especially if the natural hosts are genetically difficult to handle, slow growing, unculturable, or even unknown. We describe a straightforward strategy that combines the power of advanced DNA engineering (recombiogenic cloning) in Escherichia coli with the utility of pseudomonads as the heterologous host for the analysis and mutagenesis of known and unknown secondary metabolite pathways. The myxochromide S biosynthetic gene cluster from Stigmatella aurantiaca was rebuilt and engineered in E. coli to contain the elements required for expression in pseudomonads. The successful production in Pseudomonas putida, at unprecedented levels, demonstrates the feasibility of the new approach to the analysis and mutagenesis of these important pathways.
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98
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Testa G, Schaft J, van der Hoeven F, Glaser S, Anastassiadis K, Zhang Y, Hermann T, Stremmel W, Stewart AF. A reliable lacZ expression reporter cassette for multipurpose, knockout-first alleles. Genesis 2004; 38:151-8. [PMID: 15048813 DOI: 10.1002/gene.20012] [Citation(s) in RCA: 171] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Alteration of the mouse genome through homologous recombination in embryonic stem (ES) cells is the most accurate and versatile way to dissect gene function in a vertebrate model. Most often, a selectable marker is used to create a knockout allele by replacing an essential part of the gene. However, knockout strategies are limited because the mutation is present constitutively. Conditional approaches based on the Cre-loxP site-specific recombination (SSR) system address this limitation; however, it requires that all parts of the targeted gene remain in ES cells. Here we report success with a "knockout-first" strategy that ablates gene function by insertion of RNA processing signals without deletion of any of the target gene. Incorporation of site-specific recombination target sites creates a multipurpose allele for both knockout and conditional applications.
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99
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Auwerx J, Avner P, Baldock R, Ballabio A, Balling R, Barbacid M, Berns A, Bradley A, Brown S, Carmeliet P, Chambon P, Cox R, Davidson D, Davies K, Duboule D, Forejt J, Granucci F, Hastie N, de Angelis MH, Jackson I, Kioussis D, Kollias G, Lathrop M, Lendahl U, Malumbres M, von Melchner H, Müller W, Partanen J, Ricciardi-Castagnoli P, Rigby P, Rosen B, Rosenthal N, Skarnes B, Stewart AF, Thornton J, Tocchini-Valentini G, Wagner E, Wahli W, Wurst W. The European dimension for the mouse genome mutagenesis program. Nat Genet 2004; 36:925-7. [PMID: 15340424 PMCID: PMC2716028 DOI: 10.1038/ng0904-925] [Citation(s) in RCA: 167] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The European Mouse Mutagenesis Consortium is the European initiative contributing to the international effort on functional annotation of the mouse genome. Its objectives are to establish and integrate mutagenesis platforms, gene expression resources, phenotyping units, storage and distribution centers and bioinformatics resources. The combined efforts will accelerate our understanding of gene function and of human health and disease.
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100
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Vintersten K, Testa G, Stewart AF. Microinjection of BAC DNA into the pronuclei of fertilized mouse oocytes. METHODS IN MOLECULAR BIOLOGY (CLIFTON, N.J.) 2004; 256:141-58. [PMID: 15024165 DOI: 10.1385/1-59259-753-x:141] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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