Disruption of a silencer domain by a retrotransposon.

Genetics ◽  
1992 ◽  
Vol 131 (3) ◽  
pp. 519-529 ◽  
Author(s):  
M F Mastrangelo ◽  
K G Weinstock ◽  
B K Shafer ◽  
A M Hedge ◽  
D J Garfinkel ◽  
...  
Keyword(s):  
Gene Silencing ◽  
Induced Mutations ◽  
Ty Element ◽  
Alpha Factor ◽  
Resistant Mutants ◽  
Derivatives Of ◽  
His3 Gene

Abstract A galactose-inducible Ty element carrying the HIS3 gene has been used as an insertional mutagen to generate alpha-factor resistant mutants. This collection of Ty-induced mutations includes insertions into the gene for the alpha-factor receptor (STE2), several nonspecific STE genes, and mutations that lead to the expression of the normally silent HML alpha locus. The hml alpha "on" mutations fall into two classes, those that disrupt trans-acting regulators involved in silencing HML alpha and a novel class of mutations that activate HML alpha by insertion at that locus. The hml alpha::Ty "on" mutations illustrate the unusual ability of these retrotransposons to activate genes by overcoming gene silencing mechanisms. The hml alpha::Ty "on" mutations include examples of multimeric Ty arrays. Single Ty and solo delta insertion derivatives of these Ty multimers restore the ability of the silencing mechanism to repress HML alpha.

Restriction of P-element insertions at the Notch locus of Drosophila melanogaster

1987 ◽  
Vol 7 (4) ◽  
pp. 1545-1548
Author(s):  
M R Kelley ◽  
S Kidd ◽  
R L Berg ◽  
M W Young
Keyword(s):  
Drosophila Melanogaster ◽  
Dna Sequences ◽  
Consensus Sequence ◽  
P Element ◽  
Induced Mutations ◽  
P Elements ◽  
Target Dna ◽  
Complex Locus ◽  
Additional Level ◽  
Derivatives Of

P elements move about the Drosophila melanogaster genome in a nonrandom fashion, preferring some chromosomal targets for insertion over others (J. C. J. Eeken, F. H. Sobels, V. Hyland, and A. P. Schalet, Mutat. Res. 150:261-275, 1985; W. R. Engels, Annu. Rev. Genet. 17:315-344, 1983; M. D. Golubovsky, Y. N. Ivanov, and M. M. Green, Proc. Natl. Acad. Sci. USA 74:2973-2975, 1977; M. J. Simmons and J. K. Lim, Proc. Natl. Acad. Sci. USA 77:6042-6046, 1980). Some of this specificity may be due to recognition of a particular DNA sequence in the target DNA; derivatives of an 8-base-pair consensus sequence are occupied by these transposable elements at many different chromosomal locations (K. O'Hare and G. M. Rubin, Cell 34:25-36, 1983). An additional level of specificity of P-element insertions is described in this paper. Of 14 mutations induced in the complex locus Notch by hybrid dysgenesis, 13 involved P-element insertions at or near the transcription start site of the gene. This clustering was not seen in other transposable element-induced mutations of Notch. DNA sequences homologous to the previously described consensus target for P-element insertion are not preferentially located in this region of the locus. The choice of a chromosomal site for integration appears to be based on more subtle variations in chromosome structure that are probably associated with activation or expression of the target gene.

scholarly journals TGIF1 Gene Silencing in Tendon-Derived Stem Cells Improves the Tendon-to-Bone Insertion Site Regeneration

2015 ◽  
Vol 37 (6) ◽  
pp. 2101-2114 ◽  
Author(s):  
Liyang Chen ◽  
Chaoyin Jiang ◽  
Shashi Ranjan Tiwari ◽  
Amrit Shrestha ◽  
Pengcheng Xu ◽  
...  
Keyword(s):  
Stem Cells ◽  
Gene Silencing ◽  
Healing Process ◽  
Insertion Site ◽  
Tendon Repair ◽  
Scar Tissue ◽  
Connective Tissues ◽  
Expression Rate ◽  
Low Levels ◽  
Derivatives Of

Background/Aims: The slow healing process of tendon-to-bone junctions can be accelerated via implanted tendon-derived stem cells (TDSCs) with silenced transforming growth interacting factor 1 (TGIF1) gene. Tendon-to-bone insertion site is the special form of connective tissues derivatives of common connective progenitors, where TGF-β plays bidirectional effects (chondrogenic or fibrogenic) through different signaling pathways at different stages. A recent study revealed that TGF-β directly induces the chondrogenic gene Sox9. However, TGIF1 represses the expression of the cartilage master Sox9 gene and changes its expression rate against the fibrogenesis gene Scleraxis (Scx). Methods: TGIF1 siRNA was transduced or TGIF1 was over-expressed in tendon-derived stem cells. Following suprapinatus tendon repair, rats were either treated with transduced TDSCs or nontransduced TDSCs. Histologic examination and Western blot were performed in both groups. Results: In this study, the silencing of TGIF1 significantly upregulated the chondrogenic genes and markers. Similarly, TGIF1 inhibited TDSC differentiation into cartilage via interactions with TGF-β-activated Smad2 and suppressed the phosphorylation of Smad2. The area of fibrocartilage at the tendon-bone interface was significantly increased in the TGIF1 (-) group compared with the control and TGIF1-overexpressing groups in the early stages of the animal model. The interface between the tendon and bone showed a increase of new bone and fibrocartilage in the TGIF1 (-) group at 4 weeks. Fibrovascular scar tissue was observed in the TGIF1-overexpressing group and the fibrin glue only group. Low levels of fibrocartilage and fibrovascular scar tissue were found in the TDSCs group. Conclusion: Collectively, this study shows that the tendon-derived stem cell modified with TGIF1 gene silencing has promising effects on tendon-to-bone healing which can be further explored as a therapeutic tool in regenerative medicine.

Mutation to auxotrophy and prototrophy as related to symbiotic effectiveness in Rhizobium leguminosarum and R. trifolii

1969 ◽  
Vol 15 (6) ◽  
pp. 611-622 ◽  
Author(s):  
E. A. Schwinghamer
Keyword(s):  
Rhizobium Leguminosarum ◽  
Auxotrophic Mutant ◽  
Metabolic Inhibitors ◽  
Nutritional Requirement ◽  
Metabolic Defects ◽  
Resistant Mutants ◽  
The Relationship ◽  
Derivatives Of ◽  
Very High

Auxotrophs were isolated from four effective strains of Rhizobium leguminosarum and R. trifolii for a study of the relationship between metabolic defects and loss of ability for symbiosis. Most auxotrophs were isolated indirectly by prior isolation of mutants for resistance to metabolic inhibitors, especially D-alanine and D-histidine. The likelihood of some nutritional requirement was greatly increased among such resistant mutants, and was very high for derivatives of the R. trifolii strains. The complexity of growth factor requirement varied greatly between auxotrophs, and few had simple requirements. The most common requirement was for vitamins, notably thiamine. Partial or full restoration of effectiveness in symbiosis often accompanied reversion to prototrophy in some ineffective auxotrophs. The frequency of some degree of restoration among prototrophs varied from 0% to 100%, depending on the auxotrophic mutant involved. In one ineffective auxotroph of R. trifolii strain T1 the level of reversion (partial to complete) in vitro varied considerably and generally paralleled the degree of restoration of effectiveness. Biochemical deficiency appeared to be meaningfully related to impaired symbiosis in some auxotrophs but the relationship was probably incidental in most others. These auxotroph–prototroph studies are considered from the standpoint of relationship to several areas of research on Rhizobium.

scholarly journals Host-induced avirulence of hibiscus chlorotic ringspot virus mutants correlates with reduced gene-silencing suppression activity

2006 ◽  
Vol 87 (2) ◽  
pp. 451-459 ◽  
Author(s):  
Chunying Meng ◽  
Jun Chen ◽  
Jinrong Peng ◽  
Sek-Man Wong
Keyword(s):  
Gene Silencing ◽  
Green Fluorescence Protein ◽  
Potato Virus X ◽  
Serial Passage ◽  
Ringspot Virus ◽  
Transcriptional Gene Silencing ◽  
Turnip Crinkle Virus ◽  
Induced Mutations ◽  
Post Transcriptional Gene Silencing ◽  
Local Lesion Host

Post-transcriptional gene silencing (PTGS) and virus-encoded gene-silencing suppressors are defence and counterdefence strategies developed by host and pathogens during evolution. Using a green fluorescence protein-based transient suppression system, the coat protein (CP) of Hibiscus chlorotic ringspot virus (HCRSV) was identified as a strong gene-silencing suppressor. CP suppressed sense RNA-induced but not dsRNA-induced local and systemic PTGS. This is different from another virus in the genus Carmovirus, Turnip crinkle virus (TCV), the CP of which strongly suppresses dsRNA-induced PTGS. HCRSV CP domain deletion mutants lost their suppression function, indicating that the complete CP is essential for suppression of PTGS. When CP was expressed from a Potato virus X (PVX) vector, it was able to enhance the symptom severity and to increase the accumulation of PVX RNA. Here, it is proposed that HCRSV CP suppresses PTGS at the initiation step, which is different from TCV CP. In addition, a previous study demonstrated that CP mutants resulting from serial passage of HCRSV in its local lesion host also showed a significantly reduced suppression function, indicating that host-induced mutations that lead to avirulence of HCRSV in kenaf correlate with its reduced ability to suppress PTGS.

scholarly journals Restriction of P-element insertions at the Notch locus of Drosophila melanogaster.

1987 ◽  
Vol 7 (4) ◽  
pp. 1545-1548 ◽  
Author(s):  
M R Kelley ◽  
S Kidd ◽  
R L Berg ◽  
M W Young
Keyword(s):  
Drosophila Melanogaster ◽  
Dna Sequences ◽  
Consensus Sequence ◽  
P Element ◽  
Induced Mutations ◽  
P Elements ◽  
Target Dna ◽  
Complex Locus ◽  
Additional Level ◽  
Derivatives Of

P elements move about the Drosophila melanogaster genome in a nonrandom fashion, preferring some chromosomal targets for insertion over others (J. C. J. Eeken, F. H. Sobels, V. Hyland, and A. P. Schalet, Mutat. Res. 150:261-275, 1985; W. R. Engels, Annu. Rev. Genet. 17:315-344, 1983; M. D. Golubovsky, Y. N. Ivanov, and M. M. Green, Proc. Natl. Acad. Sci. USA 74:2973-2975, 1977; M. J. Simmons and J. K. Lim, Proc. Natl. Acad. Sci. USA 77:6042-6046, 1980). Some of this specificity may be due to recognition of a particular DNA sequence in the target DNA; derivatives of an 8-base-pair consensus sequence are occupied by these transposable elements at many different chromosomal locations (K. O'Hare and G. M. Rubin, Cell 34:25-36, 1983). An additional level of specificity of P-element insertions is described in this paper. Of 14 mutations induced in the complex locus Notch by hybrid dysgenesis, 13 involved P-element insertions at or near the transcription start site of the gene. This clustering was not seen in other transposable element-induced mutations of Notch. DNA sequences homologous to the previously described consensus target for P-element insertion are not preferentially located in this region of the locus. The choice of a chromosomal site for integration appears to be based on more subtle variations in chromosome structure that are probably associated with activation or expression of the target gene.

Large chromosomal inversion correlated with spectinomycin resistance in Lactococcus lactis subsp. lactis bv. diacetylactis S50

2008 ◽  
Vol 54 (2) ◽  
pp. 143-149 ◽  
Author(s):  
Milan Kojic ◽  
Branko Jovcic ◽  
Jelena Begovic ◽  
Djordje Fira ◽  
Ljubisa Topisirovic
Keyword(s):  
Lactococcus Lactis ◽  
Chromosomal Inversion ◽  
High Concentration ◽  
Lactococcus Lactis Subsp ◽  
Ribosomal Operons ◽  
One Step ◽  
Resistant Mutants ◽  
High Concentrations ◽  
Derivatives Of

A large chromosomal inversion that confers resistance to high concentrations of the antibiotic spectinomycin in Lactococcus lactis subsp. lactis bv. diacetylactis S50 was identified by pulsed field gel electrophoresis. The same type of inversion was identified in 4 independent experiments and in 4 different derivatives of strain S50, indicating the same position and the same mechanism of recombination as a response to antibiotic selective pressure in all derivatives. An analysis of ribosomal operons in strain S50 and mutants revealed that ribosomal operons are not endpoints of the recombination. Spectinomycin-resistant mutants appeared in a population of S50 derivatives at a high frequency of 2 × 10−7. These spectinomycin-resistant mutants were not able to compete successfully with the wild-type strain during 25 generations (48 h) of co-culture in vitro, indicating that inversion had a significant fitness cost. Results demonstrate that as a mechanism of genome plasticity, inversion can be directly involved in one-step development of the adaptation to a high concentration of spectinomycin.

Multimeric arrays of the yeast retrotransposon Ty

1990 ◽  
Vol 10 (6) ◽  
pp. 2882-2892
Author(s):  
K G Weinstock ◽  
M F Mastrangelo ◽  
T J Burkett ◽  
D J Garfinkel ◽  
J N Strathern
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Structural Analysis ◽  
Long Terminal Repeat ◽  
Terminal Repeat ◽  
Target Sequence ◽  
Direct Repeats ◽  
Ty Elements ◽  
Resistant Mutants ◽  
His3 Gene ◽  
Yeast Retrotransposon

We have identified a novel integrated form of the yeast retrotransposon Ty consisting of multiple elements joined into large arrays. These arrays were first identified among Ty-induced alpha-pheromone-resistant mutants of MATa cells of Saccharomyces cerevisiae which contain Ty insertions at HML alpha that result in the expression of that normally silent cassette. These insertions are multimeric arrays of both the induced genetically marked Ty element and unmarked Ty elements. Structural analysis of the mutations indicated that the arrays include tandem direct repeats of Ty elements separated by only a single long terminal repeat. The Ty-HML junction fragments of one mutant were cloned and shown to contain a 5-base-pair duplication of the target sequence that is characteristic of a Ty transpositional insertion. In addition, the arrays include rearranged Ty elements that do not have normal long terminal repeat junctions. We have also identified multimeric Ty insertions at other chromosomal sites and as insertions that allow expression of a promoterless his3 gene on a plasmid. The results suggest that Ty transposition includes an intermediate that can undergo recombination to produce multimers.

scholarly journals Multimeric arrays of the yeast retrotransposon Ty.

1990 ◽  
Vol 10 (6) ◽  
pp. 2882-2892 ◽  
Author(s):  
K G Weinstock ◽  
M F Mastrangelo ◽  
T J Burkett ◽  
D J Garfinkel ◽  
J N Strathern
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Structural Analysis ◽  
Long Terminal Repeat ◽  
Terminal Repeat ◽  
Target Sequence ◽  
Direct Repeats ◽  
Ty Elements ◽  
Resistant Mutants ◽  
His3 Gene ◽  
Yeast Retrotransposon

We have identified a novel integrated form of the yeast retrotransposon Ty consisting of multiple elements joined into large arrays. These arrays were first identified among Ty-induced alpha-pheromone-resistant mutants of MATa cells of Saccharomyces cerevisiae which contain Ty insertions at HML alpha that result in the expression of that normally silent cassette. These insertions are multimeric arrays of both the induced genetically marked Ty element and unmarked Ty elements. Structural analysis of the mutations indicated that the arrays include tandem direct repeats of Ty elements separated by only a single long terminal repeat. The Ty-HML junction fragments of one mutant were cloned and shown to contain a 5-base-pair duplication of the target sequence that is characteristic of a Ty transpositional insertion. In addition, the arrays include rearranged Ty elements that do not have normal long terminal repeat junctions. We have also identified multimeric Ty insertions at other chromosomal sites and as insertions that allow expression of a promoterless his3 gene on a plasmid. The results suggest that Ty transposition includes an intermediate that can undergo recombination to produce multimers.

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