scholarly journals The role of insulators in transgene transvection inDrosophila

2019 ◽  
Author(s):  
Pawel Piwko ◽  
Ilektra Vitsaki ◽  
Ioannis Livadaras ◽  
Christos Delidakis
Keyword(s):  
Homologous Chromosome ◽  
Genetic Locus ◽  
Optimal Configuration ◽  
Transcriptional Enhancer ◽  
Gypsy Insulator ◽  
Insulator Element

AbstractTransvection is the phenomenon where a transcriptional enhancer activates a promoter located on the homologous chromosome. It has been amply documented inDrosophilawhere homologues are closely paired in most, if not all, somatic nuclei, but it has been known to rarely occur in mammals as well. We have taken advantage of site-directed transgenesis to insert reporter constructs into the same genetic locus inDrosophilaand have evaluated their ability to engage in transvection by testing many heterozygous combinations. We find that transvection requires the presence of an insulator element on both homologues. Homotypictrans-interactions between four different insulators can support transvection: thegypsy insulator(GI),Wari, Fab-8and1A2;GIandFab-8are more effective thanWarior1A2. We show that in the presence of insulators, transvection displays the characteristics that have been previously described: it requires homologue pairing, but can happen at any of several loci in the genome; a solitary enhancer confronted with an enhancerless reporter is sufficient to drive transcription; it is weaker than the action of the same enhancer-promoter pair incisand it is further suppressed bycis-promoter competition. Though necessary, the presence of homotypic insulators is not sufficient for transvection; their position, number and orientation matters. A single GI adjacent to both enhancer and promoter is the optimal configuration. The addition of a heterologous insulator in one homolog can positively or negatively influence transvection strength. The local landscape of enhancers and promoters is also important, indicative of complex insulator-enhancer-promoter interactions.

Drosophila brachyenteron regulates gene activity and morphogenesis in the gut

Development ◽  
1996 ◽  
Vol 122 (12) ◽  
pp. 3707-3718 ◽  
Author(s):  
J.B. Singer ◽  
R. Harbecke ◽  
T. Kusch ◽  
R. Reuter ◽  
J.A. Lengyel
Keyword(s):  
Genetic Locus ◽  
Malpighian Tubules ◽  
Gene Activity ◽  
Phenotypic Characterization ◽  
Gut Development ◽  
Allelic Series ◽  
Genes Encoding

Chromosomal region 68D/E is required for various aspects of Drosophila gut development; within this region maps the Brachyury homolog T-related gene (Trg), DNA of which rescues the hindgut defects of deficiency 68D/E. From a screen of 13,000 mutagenized chromosomes we identified six non-complementing alleles that are lethal over deficiencies of 68D/E and show a hindgut phenotype. These mutations constitute an allelic series and are all rescued to viability by a Trg transgene. We have named the mutant alleles and the genetic locus they define brachyenteron (byn); phenotypic characterization of the strongest alleles allows determination of the role of byn in embryogenesis. byn expression is activated by tailless, but byn does not regulate itself. byn expression in the hindgut and anal pad primordia is required for the regulation of genes encoding transcription factors (even-skipped, engrailed, caudal, AbdominalB and orthopedia) and cell signaling molecules (wingless and decapentaplegic). In byn mutant embryos, the defective program of gene activity in these primordia is followed by apoptosis (initiated by reaper expression and completed by macrophage engulfment), resulting in severely reduced hindgut and anal pads. Although byn is not expressed in the midgut or the Malpighian tubules, it is required for the formation of midgut constrictions and for the elongation of the Malpighian tubules.

Homologous chromosome pairing in meiosis of higher eukaryotes—still an enigma?

Genome ◽  
2020 ◽  
Vol 63 (10) ◽  
pp. 469-482
Author(s):  
J. Sybenga
Keyword(s):  
Chromosome Pairing ◽  
Dna Sequences ◽  
Homologous Chromosome ◽  
Homology Search ◽  
Size Difference ◽  
Primary Role ◽  
Dna Double Strand Breaks ◽  
Homologous Chromosome Pairing ◽  
Higher Eukaryotes

Meiosis is the basis of the generative reproduction of eukaryotes. The crucial first step is homologous chromosome pairing. In higher eukaryotes, micrometer-scale chromosomes, micrometer distances apart, are brought together by nanometer DNA sequences, at least a factor of 1000 size difference. Models of homology search, homologue movement, and pairing at the DNA level in higher eukaryotes are primarily based on studies with yeast where the emphasis is on the induction and repair of DNA double-strand breaks (DSB). For such a model, the very large nuclei of most plants and animals present serious problems. Homology search without DSBs cannot be explained by models based on DSB repair. The movement of homologues to meet each other and make contact at the molecular level is not understood. These problems are discussed and the conclusion is that at present practically nothing is known of meiotic homologue pairing in higher eukaryotes up to the formation of the synaptonemal complex, and that new, necessarily speculative models must be developed. Arguments are given that RNA plays a central role in homology search and a tentative model involving RNA in homology search is presented. A role of actin in homologue movement is proposed. The primary role of DSBs in higher eukaryotes is concluded to not be in pairing but in the preparation of Holliday junctions, ultimately leading to chromatid exchange.

scholarly journals Identification of a genetic locus controlling bacteria-driven colitis and associated cancer through effects on innate inflammation

2012 ◽  
Vol 209 (7) ◽  
pp. 1309-1324 ◽  
Author(s):  
Olivier Boulard ◽  
Stefanie Kirchberger ◽  
Daniel J. Royston ◽  
Kevin J. Maloy ◽  
Fiona M. Powrie
Keyword(s):  
Cancer Susceptibility ◽  
Association Studies ◽  
Genetic Locus ◽  
Lymphoid Cells ◽  
Helicobacter Hepaticus ◽  
Colon Inflammation ◽  
Model Combining ◽  
Congenic Interval ◽  
Genetic Interval

Chronic inflammation of the intestine has been associated with an elevated risk of developing colorectal cancer. Recent association studies have highlighted the role of genetic predisposition in the etiology of colitis and started to unravel its complexity. However, the genetic factors influencing the progression from colon inflammation to tumorigenesis are not known. We report the identification of a genetic interval Hiccs that regulates Helicobacter hepaticus–induced colitis and associated cancer susceptibility in a 129.RAG−/− mouse model. The 1.7-Mb congenic interval on chromosome 3, containing eight genes and five microRNAs, renders susceptible mice resistant to colitis and reduces tumor incidence and multiplicity. Bone marrow chimera experiments showed that resistance is conferred by the hematopoietic compartment. Moreover, the Hiccs locus controls the induction of the innate inflammatory response by regulating cytokine expression and granulocyte recruitment by Thy1+ innate lymphoid cells. Using a tumor-promoting model combining chronic Helicobacter hepaticus infection and the carcinogen azoxymethane, we found that Hiccs also regulates the frequency of colitis-associated neoplasia. Our study highlights the importance of innate immune cells and their genetic configuration in driving progression from inflammation toward cancer and opens the door for analysis of these pathways in human inflammatory disorders and associated cancers.

Apolipoprotein E genotype and major depression in a community of older adults. The Cache County Study

2003 ◽  
Vol 33 (3) ◽  
pp. 541-547 ◽  
Author(s):  
D. C. STEFFENS ◽  
M. C. NORTON ◽  
A. D. HART ◽  
I. SKOOG ◽  
C. CORCORAN ◽  
...  
Keyword(s):  
Apolipoprotein E ◽  
Late Onset ◽  
Allelic Variation ◽  
Genetic Locus ◽  
Significant Interaction Effect ◽  
Ε4 Allele ◽  
Cache County ◽  
Relationship Of ◽  
The Relationship

Background. The role of allelic variation in APOE, the genetic locus for apolipoprotein E, in geriatric depression is poorly understood. There are conflicting reports as to an association between the ε4 allele and depression in late life.Method. Using a community based study of non-demented elders in Cache County, Utah, that included many very old individuals, we examined the relationship between APOE and late-onset (age >60) depression, with particular attention to possible age effects.Results. There was no overall association between APOE and depression. However, there was a significant interaction effect of APOE and age such that the relationship of late-onset depression with respect to presence of the ε4 allele was larger among those 80 and older compared with those below age 80. Consistent with previous studies, women were more likely to experience late-onset depression than men.Conclusions. Because we excluded prevalent cases of dementia, this pattern of relative risk with age may reflect the appearance of depressive symptoms as a prodrome of Alzheimer's disease or vascular dementia. Longitudinal studies should help to confirm or refute this explanation of the data.

scholarly journals Varying the Abundance of O Antigen inRhizobium etli and Its Effect on Symbiosis withPhaseolus vulgaris

2000 ◽  
Vol 182 (19) ◽  
pp. 5317-5324 ◽  
Author(s):  
K. Dale Noel ◽  
Lennart S. Forsberg ◽  
Russell W. Carlson
Keyword(s):  
Phaseolus Vulgaris ◽  
Structural Feature ◽  
Gel Electrophoresis ◽  
Genetic Locus ◽  
Normal Amount ◽  
Wild Type ◽  
Sugar Composition ◽  
Genetic Region ◽  
O Antigen

ABSTRACT Judged by migration of its lipopolysaccharide (LPS) in gel electrophoresis, the O antigen of Rhizobium etli mutant strain CE166 was apparently of normal size. However, its LPS sugar composition and staining of the LPS bands after electrophoresis indicated that the proportion of its LPS molecules that possessed O antigen was only 40% of the wild-type value. Its LPS also differed from the wild type by lacking quinovosamine (2-amino-2,6-dideoxyglucose). Both of these defects were due to a single genetic locus carrying a Tn5 insertion. The deficiency in O-antigen amount, but not the absence of quinovosamine, was suppressed by transferring into this strain recombinant plasmids that shared a 7.8-kb stretch of the R. etli CE3lps genetic region α, even though this suppressing DNA did not carry the genetic region mutated in strain CE166. Strain CE166 gave rise to pseudonodules on legume host Phaseolus vulgaris, whereas the mutant suppressed by DNA fromlps region α elicited nitrogen-fixing nodules. However, the nodules in the latter case developed slowly and were widely dispersed. Two other R. etli mutants that had one-half or less of the normal amount of O antigen also gave rise to pseudonodules on P. vulgaris. The latter strains were mutated inlps region α and could be restored to normal LPS content and normal symbiosis by complementation with wild-type DNA from this region. Hence, the symbiotic role of LPS requires near-normal abundance of O antigen and may require a structural feature conferred by quinovosamine.

scholarly journals Genetic Basis for Lipopolysaccharide O-Antigen Biosynthesis in Bordetellae

1999 ◽  
Vol 67 (8) ◽  
pp. 3763-3767 ◽  
Author(s):  
Andrew Preston ◽  
Andrew G. Allen ◽  
Joanna Cadisch ◽  
Richard Thomas ◽  
Kim Stevens ◽  
...  
Keyword(s):  
Insertion Sequence ◽  
Genetic Basis ◽  
Genetic Locus ◽  
Bordetella Bronchiseptica ◽  
Open Reading Frames ◽  
Bordetella Parapertussis ◽  
O Antigen ◽  
Surface Polysaccharide ◽  
Reading Frames

ABSTRACT Bordetella bronchiseptica and Bordetella parapertussis express a surface polysaccharide, attached to a lipopolysaccharide, which has been called O antigen. This structure is absent from Bordetella pertussis. We report the identification of a large genetic locus in B. bronchiseptica and B. parapertussis that is required for O-antigen biosynthesis. The locus is replaced by an insertion sequence in B. pertussis, explaining the lack of O-antigen biosynthesis in this species. The DNA sequence of the B. bronchiseptica locus has been determined and the presence of 21 open reading frames has been revealed. We have ascribed putative functions to many of these open reading frames based on database searches. Mutations in the locus in B. bronchiseptica andB. parapertussis prevent O-antigen biosynthesis and provide tools for the study of the role of O antigen in infections caused by these bacteria.

scholarly journals Complex Interplay of theUL136Isoforms Balances Cytomegalovirus Replication and Latency

mBio ◽  
2016 ◽  
Vol 7 (2) ◽  
Author(s):  
Katie Caviness ◽  
Farah Bughio ◽  
Lindsey B. Crawford ◽  
Daniel N. Streblow ◽  
Jay A. Nelson ◽  
...  
Keyword(s):  
Virus Replication ◽  
Human Cytomegalovirus ◽  
Secretory Pathway ◽  
Hcmv Infection ◽  
Genetic Locus ◽  
Protein Isoforms ◽  
Hematopoietic Progenitor Cell ◽  
Transplant Patients

ABSTRACTHuman cytomegalovirus (HCMV), a betaherpesvirus, persists indefinitely in the human host through poorly understood mechanisms. TheUL136gene is carried within a genetic locus important to HCMV latency termed theUL133/8locus, which also carriesUL133,UL135, andUL138. Previously, we demonstrated thatUL136is expressed as five protein isoforms ranging from 33-kDa to 19-kDa, arising from alternative transcription and, likely, translation initiation mechanisms. We previously showed that theUL136isoforms are largely dispensable for virus infection in fibroblasts, a model for productive virus replication. In our current work,UL136has emerged as a complex regulator of HCMV infection in multiple contexts of infection relevant to HCMV persistence: in an endothelial cell (EC) model of chronic infection, in a CD34+hematopoietic progenitor cell (HPC) model of latency, and in anin vivoNOD-scidIL2Rγcnullhumanized (huNSG) mouse model for latency. The 33- and 26-kDa isoforms promote replication, while the 23- and 19-kDa isoforms suppress replication in ECs, in CD34+HPCs, and in huNSG mice. The role of the 25-kDa isoform is context dependent and influences the activity of the other isoforms. These isoforms localize throughout the secretory pathway, and loss of the 33- and 26-kDaUL136isoforms results in virus maturation defects in ECs. This work reveals an intriguing functional interplay between protein isoforms that impacts virus replication, latency, and dissemination, contributing to the overall role of theUL133/8locus in HCMV infection.IMPORTANCEThe persistence of DNA viruses, and particularly of herpesviruses, remains an enigma because we have not completely defined the viral and host factors important to persistence. Human cytomegalovirus, a herpesvirus, persists in the absence of disease in immunocompetent individuals but poses a serious disease threat to transplant patients and the developing fetus. There is no vaccine, and current therapies do not target latent reservoirs. In an effort to define the viral factors important to persistence, we have studied viral genes with no known viral replication function in contexts important to HCMV persistence. Using models relevant to viral persistence, we demonstrate opposing roles of protein isoforms encoded by theUL136gene in regulating latent and replicative states of infection. Our findings reveal an intriguing interplay betweenUL136protein isoforms and defineUL136as an important regulator of HCMV persistence.

scholarly journals Thec-myc Insulator Element and Matrix Attachment Regions Definethe c-myc ChromosomalDomain

2003 ◽  
Vol 23 (24) ◽  
pp. 9338-9348 ◽  
Author(s):  
Wendy M. Gombert ◽  
Stephen D. Farris ◽  
Eric D. Rubio ◽  
Kristin M. Morey-Rosler ◽  
William H. Schubach ◽  
...  
Keyword(s):  
Transcription Unit ◽  
Matrix Attachment Regions ◽  
Functional Activities ◽  
Insulator Element ◽  
Evolutionarily Conserved ◽  
Blocking Activity ◽  
Enhancer Blocking ◽  
Insulator Elements ◽  
Flanking Regions

ABSTRACT Insulator elements and matrix attachment regions are essential for the organization of genetic information within the nucleus. By comparing the pattern of histone modifications at the mouse and human c-myc alleles, we identified an evolutionarily conserved boundary at which the c-myc transcription unit is separated from the flanking condensed chromatin enriched in lysine 9-methylated histone H3. This region harbors the c-myc insulator element (MINE), which contains at least two physically separable, functional activities: enhancer-blocking activity and barrier activity. The enhancer-blocking activity is mediated by CTCF. Chromatin immunoprecipitation assays demonstrate that CTCF is constitutively bound at the insulator and at the promoter region independent of the transcriptional status of c-myc. This result supports an architectural role of CTCF rather than a regulatory role in transcription. An additional higher-order nuclear organization of the c-myc locus is provided by matrix attachment regions (MARs) that define a domain larger than 160 kb. The MARs of the c-myc domain do not act to prevent the association of flanking regions with lysine 9-methylated histones, suggesting that they do not function as barrier elements.

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