scholarly journals A similar gene is shared by both the variant surface glycoprotein and procyclin gene transcription units of Trypanosoma brucei

1991 ◽  
Vol 11 (3) ◽  
pp. 1473-1479
Author(s):  
M Berberof ◽  
A Pays ◽  
E Pays
Keyword(s):  
Gene Expression ◽  
Life Cycle ◽  
Trypanosoma Brucei ◽  
Gene Transcription ◽  
Transcription Unit ◽  
Surface Glycoprotein ◽  
Variant Surface Glycoprotein ◽  
Polycistronic Transcription ◽  
Expression Site ◽  
Similar Gene

The genes for the variant surface glycoprotein (VSG) and procyclin are expressed in a mutually exclusive manner during the life cycle of Trypanosoma brucei and synthesize the most abundant mRNAs specific to the bloodstream and procyclic stages of the parasite, respectively. Genes belonging to the polycistronic transcription unit of the VSG gene (expression site-associated genes [ESAGs]) are uniquely expressed in the bloodstream form, but some members of ESAG families (genes related to ESAGs [GRESAGs]) are independently transcribed outside the VSG gene expression site. We report here that a gene related to ESAG 2, GRESAG 2.1, is present and expressed in a procyclin gene transcription unit (PARP A locus), which is polycistronic. Members of the ESAG 2 family are thus present in the two major differentially stage-regulated transcription units of this parasite.

scholarly journals A similar gene is shared by both the variant surface glycoprotein and procyclin gene transcription units of Trypanosoma brucei.

1991 ◽  
Vol 11 (3) ◽  
pp. 1473-1479 ◽  
Author(s):  
M Berberof ◽  
A Pays ◽  
E Pays
Keyword(s):  
Gene Expression ◽  
Life Cycle ◽  
Trypanosoma Brucei ◽  
Gene Transcription ◽  
Transcription Unit ◽  
Surface Glycoprotein ◽  
Variant Surface Glycoprotein ◽  
Polycistronic Transcription ◽  
Expression Site ◽  
Similar Gene

The genes for the variant surface glycoprotein (VSG) and procyclin are expressed in a mutually exclusive manner during the life cycle of Trypanosoma brucei and synthesize the most abundant mRNAs specific to the bloodstream and procyclic stages of the parasite, respectively. Genes belonging to the polycistronic transcription unit of the VSG gene (expression site-associated genes [ESAGs]) are uniquely expressed in the bloodstream form, but some members of ESAG families (genes related to ESAGs [GRESAGs]) are independently transcribed outside the VSG gene expression site. We report here that a gene related to ESAG 2, GRESAG 2.1, is present and expressed in a procyclin gene transcription unit (PARP A locus), which is polycistronic. Members of the ESAG 2 family are thus present in the two major differentially stage-regulated transcription units of this parasite.

A gene from the variant surface glycoprotein expression site encodes one of several transmembrane adenylate cyclases located on the flagellum of Trypanosoma brucei

1992 ◽  
Vol 12 (3) ◽  
pp. 1218-1225
Author(s):  
P Paindavoine ◽  
S Rolin ◽  
S Van Assel ◽  
M Geuskens ◽  
J C Jauniaux ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Trypanosoma Brucei ◽  
Membrane Fraction ◽  
Transcription Unit ◽  
Bloodstream Form ◽  
Surface Glycoprotein ◽  
Yeast Cells ◽  
Variant Surface Glycoprotein ◽  
Polycistronic Transcription ◽  
Expression Site

The bloodstream form of Trypanosoma brucei contains transcripts of at least four genes showing partial sequence homology to the genes for eucaryotic adenylate and guanylate cyclases (S. Alexandre, P. Paindavoine, P. Tebabi, A. Pays, S. Halleux, M. Steinert, and E. Pays, Mol. Biochem. Parasitol. 43:279-288, 1990). One of these genes, termed ESAG 4, belongs to the polycistronic transcription unit of the variant surface glycoprotein (VSG) gene. Whereas ESAG 4 is transcribed only in the bloodstream form of the parasite, the three other genes, GRESAG 4.1, 4.2, and 4.3, are also expressed in procyclic (insect) forms. These genes differ primarily in a region presumed to encode a large extracellular domain. We show here that ESAG 4-related glycoproteins of about 150 kDa can be found in the trypanosome membrane, that they are detected, by light and electron gold immunocytochemistry, only at the surface of the flagellum, and that the products of at least two of these genes, ESAG 4 and GRESAG 4.1, can complement a Saccharomyces cerevisiae mutant for adenylate cyclase. The recombinant cyclases are associated with the yeast membrane fraction and differ with respect to their activation by calcium: while the GRESAG 4.1 and yeast cyclases are inhibited by calcium, the ESAG 4 cyclase is stimulated. ESAG 4 thus most probably encodes the calcium-activated cyclase that has been found to be expressed only in the bloodstream form of T. brucei (S. Rolin, S. Halleux, J. Van Sande, J. E. Dumont, E. Pays, and M. Steinert. Exp. Parasitol. 71:350-352, 1990). Our data suggest that the trypanosome cyclases are not properly regulated in yeast cells.

scholarly journals A gene from the variant surface glycoprotein expression site encodes one of several transmembrane adenylate cyclases located on the flagellum of Trypanosoma brucei.

1992 ◽  
Vol 12 (3) ◽  
pp. 1218-1225 ◽  
Author(s):  
P Paindavoine ◽  
S Rolin ◽  
S Van Assel ◽  
M Geuskens ◽  
J C Jauniaux ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Trypanosoma Brucei ◽  
Membrane Fraction ◽  
Transcription Unit ◽  
Bloodstream Form ◽  
Surface Glycoprotein ◽  
Yeast Cells ◽  
Variant Surface Glycoprotein ◽  
Polycistronic Transcription ◽  
Expression Site

The bloodstream form of Trypanosoma brucei contains transcripts of at least four genes showing partial sequence homology to the genes for eucaryotic adenylate and guanylate cyclases (S. Alexandre, P. Paindavoine, P. Tebabi, A. Pays, S. Halleux, M. Steinert, and E. Pays, Mol. Biochem. Parasitol. 43:279-288, 1990). One of these genes, termed ESAG 4, belongs to the polycistronic transcription unit of the variant surface glycoprotein (VSG) gene. Whereas ESAG 4 is transcribed only in the bloodstream form of the parasite, the three other genes, GRESAG 4.1, 4.2, and 4.3, are also expressed in procyclic (insect) forms. These genes differ primarily in a region presumed to encode a large extracellular domain. We show here that ESAG 4-related glycoproteins of about 150 kDa can be found in the trypanosome membrane, that they are detected, by light and electron gold immunocytochemistry, only at the surface of the flagellum, and that the products of at least two of these genes, ESAG 4 and GRESAG 4.1, can complement a Saccharomyces cerevisiae mutant for adenylate cyclase. The recombinant cyclases are associated with the yeast membrane fraction and differ with respect to their activation by calcium: while the GRESAG 4.1 and yeast cyclases are inhibited by calcium, the ESAG 4 cyclase is stimulated. ESAG 4 thus most probably encodes the calcium-activated cyclase that has been found to be expressed only in the bloodstream form of T. brucei (S. Rolin, S. Halleux, J. Van Sande, J. E. Dumont, E. Pays, and M. Steinert. Exp. Parasitol. 71:350-352, 1990). Our data suggest that the trypanosome cyclases are not properly regulated in yeast cells.

scholarly journals DNA rearrangements associated with multiple consecutive directed antigenic switches in Trypanosoma brucei.

1996 ◽  
Vol 16 (7) ◽  
pp. 3615-3625 ◽  
Author(s):  
M Navarro ◽  
G A Cross
Keyword(s):  
Trypanosoma Brucei ◽  
Short Range ◽  
Direct Analysis ◽  
Transcription Unit ◽  
The Other ◽  
Surface Glycoprotein ◽  
Variant Surface Glycoprotein ◽  
Polycistronic Transcription ◽  
Tangible Evidence ◽  
Expression Site

Changes in variant surface glycoprotein (Vsg) expression allow Trypanosoma brucei to elude the immune response. The expressed vsg is always located at the telomeric end of a polycistronic transcription unit known as an expression site (ES). Although there are many ESs, only one is active at any particular time. The mechanisms regulating ES transcription and switching are unknown. Chromosome rearrangements within or upstream of the ES have been described to occur in occasional switch events, but no changes have been consistently associated with switching. We inserted the drug resistance genes neo and ble, conferring resistance to G418 and phleomycin, respectively, 1 kb downstream of "silent" ES promoters. This demonstrated that short-range transcription could be achieved from a silent ES promoter. From one initial transformant clone, panels of independent consecutive on-off-on switch clones were generated and analyzed. The first activation of the neo-targeted ES was always associated with deletion of the upstream tandem promoter in this ES, but no further rearrangements were detected in consecutive off-on switches of this ES. On the other hand, direct analysis of ES promoters showed that deletions and duplications occurred elsewhere. Activation of a ble-tagged 300-kb chromosome could not be achieved, but phleomycin-resistant clones could be obtained. One such clone arose from recombination between three ESs. Taken together, our experiments suggest that ES switching may occur after a period of chromosomal interactivity that may or may not leave tangible evidence in the form of detectable sequence changes.

Expression of a retroposon-like sequence upstream of the putative Trypanosoma brucei variant surface glycoprotein gene expression site promoter

1993 ◽  
Vol 13 (11) ◽  
pp. 7036-7044
Author(s):  
M J Lodes ◽  
B L Smiley ◽  
A W Stadnyk ◽  
J L Bennett ◽  
P J Myler ◽  
...  
Keyword(s):  
Gene Expression ◽  
Trypanosoma Brucei ◽  
Copy Number ◽  
Surface Glycoprotein ◽  
Variant Surface Glycoprotein ◽  
Putative Promoter ◽  
Glycoprotein Gene ◽  
Active Expression ◽  
Expression Site ◽  
Total Copy Number

We have cloned the region spanning the putative promoter from two variant surface glycoprotein gene expression sites that are at each end of chromosome M4 of Trypanosoma brucei IsTat 7. Both expression sites contain a retroposon-like sequence (ESR) pseudogene whose 3' end is approximately 30 bp upstream of the putative expression site promoter. The ESRs from both expression sites share considerable sequence homology and are related to LINE-like elements, especially the T. brucei ingi retroposon. Other ESRs are located on large, but not intermediate or mini-, chromosomes in the IsTaR 1 serodeme, and the total copy number is 10 to 20, similar to that estimated for variant surface glycoprotein expression sites. No DNA rearrangements in the vicinity of the ESR and putative expression site promoter were detected following antigenic switches in the IsTaR 1 serodeme. ESR transcripts are present in bloodstream, but not procyclic, forms. Variation in transcript size and sequence between bloodstream variant antigenic types implies that only the ESR from the active expression site is transcribed. This pattern of expression reflects that of sequences downstream of the putative expression site promoter, suggesting that the region of coordinately controlled expression extends upstream of this promoter.

scholarly journals Expression of a retroposon-like sequence upstream of the putative Trypanosoma brucei variant surface glycoprotein gene expression site promoter.

1993 ◽  
Vol 13 (11) ◽  
pp. 7036-7044 ◽  
Author(s):  
M J Lodes ◽  
B L Smiley ◽  
A W Stadnyk ◽  
J L Bennett ◽  
P J Myler ◽  
...  
Keyword(s):  
Gene Expression ◽  
Trypanosoma Brucei ◽  
Copy Number ◽  
Surface Glycoprotein ◽  
Variant Surface Glycoprotein ◽  
Putative Promoter ◽  
Glycoprotein Gene ◽  
Active Expression ◽  
Expression Site ◽  
Total Copy Number

We have cloned the region spanning the putative promoter from two variant surface glycoprotein gene expression sites that are at each end of chromosome M4 of Trypanosoma brucei IsTat 7. Both expression sites contain a retroposon-like sequence (ESR) pseudogene whose 3' end is approximately 30 bp upstream of the putative expression site promoter. The ESRs from both expression sites share considerable sequence homology and are related to LINE-like elements, especially the T. brucei ingi retroposon. Other ESRs are located on large, but not intermediate or mini-, chromosomes in the IsTaR 1 serodeme, and the total copy number is 10 to 20, similar to that estimated for variant surface glycoprotein expression sites. No DNA rearrangements in the vicinity of the ESR and putative expression site promoter were detected following antigenic switches in the IsTaR 1 serodeme. ESR transcripts are present in bloodstream, but not procyclic, forms. Variation in transcript size and sequence between bloodstream variant antigenic types implies that only the ESR from the active expression site is transcribed. This pattern of expression reflects that of sequences downstream of the putative expression site promoter, suggesting that the region of coordinately controlled expression extends upstream of this promoter.

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