scholarly journals Posttranslational control of Ty1 retrotransposition occurs at the level of protein processing.

1992 ◽  
Vol 12 (6) ◽  
pp. 2813-2825 ◽  
Author(s):  
M J Curcio ◽  
D J Garfinkel
Keyword(s):  
Protein Processing ◽  
Yeast Cells ◽  
Translational Efficiency ◽  
Gene Products ◽  
Protease Domain ◽  
High Level Expression ◽  
Gal1 Promoter ◽  
Low Levels ◽  
Ty1 Retrotransposition ◽  
High Level

High-level expression of a transpositionally competent Ty1 element fused to the inducible GAL1 promoter on a 2 microns plasmid (pGTy1) overcomes transpositional dormancy in Saccharomyces cerevisiae. To investigate the mechanisms controlling the rate of Ty1 retrotransposition, we quantitated transposition and Ty1 gene products in cells induced and uninduced for expression of pGTy1. The increase in Ty1 transposition was 45- to 125-fold greater than the increase in Ty1 RNA effected by pGTy1 induction. Translational efficiency of Ty1 RNA was not altered in transposition-induced cells, since p190TYA1-TYB1 protein synthesis increased in proportion to steady-state Ty1 RNA levels. Therefore, expression of a pGTy1 element increases the efficiency of Ty1 transposition at a posttranslational level. Galactose induction of pGTy1 enhanced TYA1 protein processing and allowed detection of processed TYB1 proteins, which are normally present at very low levels in uninduced cells. When the ability of genomic Ty1 elements to complement defined mutations in HIS3-marked pGTy1 elements was examined, mutations in the protease domain or certain mutations in the integrase domain failed to be complemented, but mutations in the reverse transcriptase domain were partially complemented by genomic Ty1 elements. Therefore, the activity of Ty1 elements in yeast cells may be limited by the availability of Ty1 protease and possibly integrase. These results suggest that Ty1 transposition is regulated at the level of protein processing and that this regulation is overcome by expression of a pGTy1 element.

Posttranslational control of Ty1 retrotransposition occurs at the level of protein processing

1992 ◽  
Vol 12 (6) ◽  
pp. 2813-2825
Author(s):  
M J Curcio ◽  
D J Garfinkel
Keyword(s):  
Protein Processing ◽  
Yeast Cells ◽  
Translational Efficiency ◽  
Gene Products ◽  
Protease Domain ◽  
High Level Expression ◽  
Gal1 Promoter ◽  
Low Levels ◽  
Ty1 Retrotransposition ◽  
High Level

High-level expression of a transpositionally competent Ty1 element fused to the inducible GAL1 promoter on a 2 microns plasmid (pGTy1) overcomes transpositional dormancy in Saccharomyces cerevisiae. To investigate the mechanisms controlling the rate of Ty1 retrotransposition, we quantitated transposition and Ty1 gene products in cells induced and uninduced for expression of pGTy1. The increase in Ty1 transposition was 45- to 125-fold greater than the increase in Ty1 RNA effected by pGTy1 induction. Translational efficiency of Ty1 RNA was not altered in transposition-induced cells, since p190TYA1-TYB1 protein synthesis increased in proportion to steady-state Ty1 RNA levels. Therefore, expression of a pGTy1 element increases the efficiency of Ty1 transposition at a posttranslational level. Galactose induction of pGTy1 enhanced TYA1 protein processing and allowed detection of processed TYB1 proteins, which are normally present at very low levels in uninduced cells. When the ability of genomic Ty1 elements to complement defined mutations in HIS3-marked pGTy1 elements was examined, mutations in the protease domain or certain mutations in the integrase domain failed to be complemented, but mutations in the reverse transcriptase domain were partially complemented by genomic Ty1 elements. Therefore, the activity of Ty1 elements in yeast cells may be limited by the availability of Ty1 protease and possibly integrase. These results suggest that Ty1 transposition is regulated at the level of protein processing and that this regulation is overcome by expression of a pGTy1 element.

scholarly journals Structural and functional analysis of a promoter of the human granulin/epithelin gene

1996 ◽  
Vol 319 (2) ◽  
pp. 441-447 ◽  
Author(s):  
Vijay BHANDARI ◽  
Rachael DANIEL ◽  
Pheng Siew LIM ◽  
Andrew BATEMAN
Keyword(s):  
Promoter Activity ◽  
Biologically Active ◽  
Gene Products ◽  
High Level Expression ◽  
Haematopoietic Cells ◽  
Molecular Masses ◽  
Chloramphenicol Acetyltransferase Gene ◽  
High Level

Granulins (grns) or epithelins (epis) are peptides with molecular masses of approx. 6 kDa that modulate the growth of cells. The precursor for the grns/epis, which might itself be biologically active, is a secreted glycoprotein containing multiple repeats of the grn/epi motif. Grn/epi mRNA occurs widely in vivo, particularly in tissues rich in epithelial and haematopoietic cells. To understand better the role of the gene products for grn/epi it is important to determine the patterns of grn/epi gene expression and how this is regulated. To assist in this we have obtained the 5´ sequence of the human grn/epi gene, and using chimaeras of the grn/epi -5´ sequence and the chloramphenicol acetyltransferase gene we have shown a strong promoter activity associated with the 5´ sequence of the human grn/epi gene. We have further delineated regions of the 5´ sequence that confer high-level expression on the chimaeric gene.

Identification of two proteins encoded by the Saccharomyces cerevisiae GAL4 gene

1984 ◽  
Vol 4 (2) ◽  
pp. 268-275
Author(s):  
A Laughon ◽  
R Driscoll ◽  
N Wills ◽  
R F Gesteland
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Regulatory System ◽  
Wild Type ◽  
High Level Expression ◽  
Gal1 Promoter ◽  
Encoded Proteins ◽  
High Level

We placed the Saccharomyces cerevisiae GAL4 gene under control of the galactose regulatory system by fusing it to the S. cerevisiae GAL1 promoter. After induction with galactose, GAL4 is now transcribed at about 1,000-fold higher levels than in wild-type S. cerevisiae. This regulated high-level expression has enabled us to tentatively identify two GAL4-encoded proteins.

scholarly journals Identification of two proteins encoded by the Saccharomyces cerevisiae GAL4 gene.

1984 ◽  
Vol 4 (2) ◽  
pp. 268-275 ◽  
Author(s):  
A Laughon ◽  
R Driscoll ◽  
N Wills ◽  
R F Gesteland
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Regulatory System ◽  
Wild Type ◽  
High Level Expression ◽  
Gal1 Promoter ◽  
Encoded Proteins ◽  
High Level

We placed the Saccharomyces cerevisiae GAL4 gene under control of the galactose regulatory system by fusing it to the S. cerevisiae GAL1 promoter. After induction with galactose, GAL4 is now transcribed at about 1,000-fold higher levels than in wild-type S. cerevisiae. This regulated high-level expression has enabled us to tentatively identify two GAL4-encoded proteins.

scholarly journals Glucose transporter isotypes switch in T-antigen-transformed pancreatic beta cells growing in culture and in mice.

1992 ◽  
Vol 12 (1) ◽  
pp. 422-432 ◽  
Author(s):  
M Tal ◽  
B Thorens ◽  
M Surana ◽  
N Fleischer ◽  
H F Lodish ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Insulin Secretion ◽  
Glucose Transporter ◽  
Islet Cells ◽  
T Antigen ◽  
High Level Expression ◽  
Glut 1 ◽  
Secondary Tumors ◽  
Low Levels ◽  
High Level

High-level expression of the low-Km glucose transporter isoform GLUT-1 is characteristic of many cultured tumor and oncogene-transformed cells. In this study, we tested whether induction of GLUT-1 occurs in tumors in vivo. Normal mouse beta islet cells express the high-Km (approximately 20 mM) glucose transporter isoform GLUT-2 but not the low-Km (1 to 3 mM) GLUT-1. In contrast, a beta cell line derived from an insulinoma arising in a transgenic mouse harboring an insulin-promoted simian virus 40 T-antigen oncogene (beta TC3) expressed very low levels of GLUT-2 but high levels of GLUT-1. GLUT-1 protein was not detectable on the plasma membrane of islets or tumors of the transgenic mice but was induced in high amounts when the tumor-derived beta TC3 cells were grown in tissue culture. GLUT-1 expression in secondary tumors formed after injection of beta TC3 cells into mice was reduced. Thus, high-level expression of GLUT-1 in these tumor cells is characteristic of culture conditions and is not induced by the oncogenic transformation; indeed, overnight culture of normal pancreatic islets causes induction of GLUT-1. We also investigated the relationship between expression of the different glucose transporter isoforms by islet and tumor cells and induction of insulin secretion by glucose. Prehyperplastic transgenic islet cells that expressed normal levels of GLUT-2 and no detectable GLUT-1 exhibited an increased sensitivity to glucose, as evidenced by maximal insulin secretion at lower glucose concentrations, compared with that exhibited by normal islets. Further, hyperplastic islets and primary and secondary tumors expressed low levels of GLUT-2 and no detectable GLUT-1 on the plasma membrane; these cells exhibited high basal insulin secretion and responded poorly to an increase in extracellular glucose. Thus, abnormal glucose-induced secretion of insulin in prehyperplastic islets in mice was independent of changes in GLUT-2 expression and did not require induction of GLUT-1 expression.

Glucose transporter isotypes switch in T-antigen-transformed pancreatic beta cells growing in culture and in mice

1992 ◽  
Vol 12 (1) ◽  
pp. 422-432
Author(s):  
M Tal ◽  
B Thorens ◽  
M Surana ◽  
N Fleischer ◽  
H F Lodish ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Insulin Secretion ◽  
Glucose Transporter ◽  
Islet Cells ◽  
T Antigen ◽  
High Level Expression ◽  
Glut 1 ◽  
Secondary Tumors ◽  
Low Levels ◽  
High Level

High-level expression of the low-Km glucose transporter isoform GLUT-1 is characteristic of many cultured tumor and oncogene-transformed cells. In this study, we tested whether induction of GLUT-1 occurs in tumors in vivo. Normal mouse beta islet cells express the high-Km (approximately 20 mM) glucose transporter isoform GLUT-2 but not the low-Km (1 to 3 mM) GLUT-1. In contrast, a beta cell line derived from an insulinoma arising in a transgenic mouse harboring an insulin-promoted simian virus 40 T-antigen oncogene (beta TC3) expressed very low levels of GLUT-2 but high levels of GLUT-1. GLUT-1 protein was not detectable on the plasma membrane of islets or tumors of the transgenic mice but was induced in high amounts when the tumor-derived beta TC3 cells were grown in tissue culture. GLUT-1 expression in secondary tumors formed after injection of beta TC3 cells into mice was reduced. Thus, high-level expression of GLUT-1 in these tumor cells is characteristic of culture conditions and is not induced by the oncogenic transformation; indeed, overnight culture of normal pancreatic islets causes induction of GLUT-1. We also investigated the relationship between expression of the different glucose transporter isoforms by islet and tumor cells and induction of insulin secretion by glucose. Prehyperplastic transgenic islet cells that expressed normal levels of GLUT-2 and no detectable GLUT-1 exhibited an increased sensitivity to glucose, as evidenced by maximal insulin secretion at lower glucose concentrations, compared with that exhibited by normal islets. Further, hyperplastic islets and primary and secondary tumors expressed low levels of GLUT-2 and no detectable GLUT-1 on the plasma membrane; these cells exhibited high basal insulin secretion and responded poorly to an increase in extracellular glucose. Thus, abnormal glucose-induced secretion of insulin in prehyperplastic islets in mice was independent of changes in GLUT-2 expression and did not require induction of GLUT-1 expression.

High world sugar prices: is Asia’s production cycle to blame?

2010 ◽  
pp. 169-173
Author(s):  
Martin Todd
Keyword(s):  
Supply Chain ◽  
Supply And Demand ◽  
Production Cycle ◽  
Low Levels ◽  
High Level ◽  
High World

The current high world sugar prices reflect a major imbalance between global supply and demand, which has reduced stocks to very low levels. Although it remains to be seen whether prices will rise much above current values, it is clear that the supply chain will remain stretched throughout 2010 and this will help to maintain prices at a high level.

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