scholarly journals Stable variant-specific transcripts of the variant cell surface glycoprotein gene 1.8 expression site in Trypanosoma brucei.

1988 ◽  
Vol 8 (2) ◽  
pp. 854-859 ◽  
Author(s):  
C Shea ◽  
L H Van der Ploeg
Keyword(s):  
Cell Surface ◽  
Surface Glycoprotein ◽  
Minimum Size ◽  
Cell Surface Glycoprotein ◽  
Glycoprotein Gene ◽  
Variant Cell ◽  
Expression Site ◽  
Specific Mrnas ◽  
Chromosome Specific Library ◽  
Nascent Transcripts

The structure and transcriptional regulation of the 1.8 variant cell surface glycoprotein (VSG) gene expression site located on a 430-kilobase (kb) chromosome was examined in a 430-kb-chromosome-specific library. Using 32P-labeled nascent transcripts generated by nuclear run-on, we selected recombinant clones derived from the 430-kb chromosome which were coordinately activated with the 1.8 VSG gene. The results show that a repetitive region with a minimum size of 27 kb is coordinately activated with the 1.8 VSG gene. As with the 1.8 VSG gene, transcription is by RNA polymerases that are insensitive to the drug alpha-amanitin at concentrations up to 1 mg/ml. Transcription results in the generation of several stable variant-specific mRNAs. These mRNAs most likely belong to a family of repetitive expression-site-associated genes.

Stable variant-specific transcripts of the variant cell surface glycoprotein gene 1.8 expression site in Trypanosoma brucei

1988 ◽  
Vol 8 (2) ◽  
pp. 854-859
Author(s):  
C Shea ◽  
L H Van der Ploeg
Keyword(s):  
Cell Surface ◽  
Surface Glycoprotein ◽  
Minimum Size ◽  
Cell Surface Glycoprotein ◽  
Glycoprotein Gene ◽  
Variant Cell ◽  
Expression Site ◽  
Specific Mrnas ◽  
Chromosome Specific Library ◽  
Nascent Transcripts

The structure and transcriptional regulation of the 1.8 variant cell surface glycoprotein (VSG) gene expression site located on a 430-kilobase (kb) chromosome was examined in a 430-kb-chromosome-specific library. Using 32P-labeled nascent transcripts generated by nuclear run-on, we selected recombinant clones derived from the 430-kb chromosome which were coordinately activated with the 1.8 VSG gene. The results show that a repetitive region with a minimum size of 27 kb is coordinately activated with the 1.8 VSG gene. As with the 1.8 VSG gene, transcription is by RNA polymerases that are insensitive to the drug alpha-amanitin at concentrations up to 1 mg/ml. Transcription results in the generation of several stable variant-specific mRNAs. These mRNAs most likely belong to a family of repetitive expression-site-associated genes.

scholarly journals A proposed mechanism for promoter-associated DNA rearrangement events at a variant surface glycoprotein gene expression site.

1992 ◽  
Vol 12 (10) ◽  
pp. 4784-4795 ◽  
Author(s):  
K M Gottesdiener ◽  
L Goriparthi ◽  
J P Masucci ◽  
L H Van der Ploeg
Keyword(s):  
Gene Expression ◽  
Promoter Region ◽  
Protozoan Parasite ◽  
Surface Glycoprotein ◽  
Dna Rearrangement ◽  
Cell Surface Glycoprotein ◽  
Circular Dna ◽  
Glycoprotein Gene ◽  
Variant Cell ◽  
Expression Site

The expressed variant cell surface glycoprotein (VSG) gene of the protozoan parasite Trypanosoma brucei is invariably found at one of several telomeric VSG gene expression sites (ESs). The active ES in variant 118 clone 1 is found on a 1.5-Mb chromosome, and the promoter region is located more than 45 kb upstream of the VSG gene. We had previously shown that DNA rearrangement events occurred in the promoter region, specifically at inactivation of this ES (K. M. Gottesdiener, H.-M. Chung, S. L. Brown, M. G.-S. Lee, and L. H. T. Van der Ploeg, Mol. Cell. Biol. 11:2467-2477, 1991). In this report, we describe the cloning of the entire 17-kb promoter region, which revealed the presence of two identical 2.15-kb tandem promoter repeats separated by 13 kb of DNA. The two virtually identical promoter repeats both function efficiently in directing transcription in transient transfection assays in insect-form trypanosomes. We characterized the DNA rearrangement events that occur at ES inactivation, and by studying both of the reciprocal products of this recombination event, we infer that these result from direct (promoter) repeat recombination, formation of heteroduplex DNA, and a reciprocal exchange event that releases a circular DNA as a side product of the reaction. The finding of DNA recombinational events in a region of the VSG gene ES that encodes the promoter(s), and their relatively frequent occurrence at ES inactivation, suggests a possible role in ES control.

A proposed mechanism for promoter-associated DNA rearrangement events at a variant surface glycoprotein gene expression site

1992 ◽  
Vol 12 (10) ◽  
pp. 4784-4795
Author(s):  
K M Gottesdiener ◽  
L Goriparthi ◽  
J P Masucci ◽  
L H Van der Ploeg
Keyword(s):  
Gene Expression ◽  
Promoter Region ◽  
Protozoan Parasite ◽  
Surface Glycoprotein ◽  
Dna Rearrangement ◽  
Cell Surface Glycoprotein ◽  
Circular Dna ◽  
Glycoprotein Gene ◽  
Variant Cell ◽  
Expression Site

The expressed variant cell surface glycoprotein (VSG) gene of the protozoan parasite Trypanosoma brucei is invariably found at one of several telomeric VSG gene expression sites (ESs). The active ES in variant 118 clone 1 is found on a 1.5-Mb chromosome, and the promoter region is located more than 45 kb upstream of the VSG gene. We had previously shown that DNA rearrangement events occurred in the promoter region, specifically at inactivation of this ES (K. M. Gottesdiener, H.-M. Chung, S. L. Brown, M. G.-S. Lee, and L. H. T. Van der Ploeg, Mol. Cell. Biol. 11:2467-2477, 1991). In this report, we describe the cloning of the entire 17-kb promoter region, which revealed the presence of two identical 2.15-kb tandem promoter repeats separated by 13 kb of DNA. The two virtually identical promoter repeats both function efficiently in directing transcription in transient transfection assays in insect-form trypanosomes. We characterized the DNA rearrangement events that occur at ES inactivation, and by studying both of the reciprocal products of this recombination event, we infer that these result from direct (promoter) repeat recombination, formation of heteroduplex DNA, and a reciprocal exchange event that releases a circular DNA as a side product of the reaction. The finding of DNA recombinational events in a region of the VSG gene ES that encodes the promoter(s), and their relatively frequent occurrence at ES inactivation, suggests a possible role in ES control.

Characterization of VSG gene expression site promoters and promoter-associated DNA rearrangement events

1991 ◽  
Vol 11 (5) ◽  
pp. 2467-2480 ◽  
Author(s):  
K Gottesdiener ◽  
H M Chung ◽  
S D Brown ◽  
M G Lee ◽  
L H Van der Ploeg
Keyword(s):  
Transcriptional Control ◽  
Transcription Unit ◽  
Surface Glycoprotein ◽  
Dna Rearrangement ◽  
Cell Surface Glycoprotein ◽  
Polycistronic Transcription ◽  
Variant Cell ◽  
Expression Site ◽  
Simple Sequence

The expressed variant cell surface glycoprotein (VSG) gene of Trypanosoma brucei is located at the 3' end of a large, telomeric, polycistronic transcription unit or expression site. We show that the region 45 kb upstream of the VSG gene, in the expression site on a 1.5-Mb chromosome, contains at least two promoters that are arranged in tandem, directing the transcription of the expression site. DNA rearrangement events occur specifically, at inactivation of the expression site, and these events delete the most upstream transcribed region and replace it with a large array of simple-sequence DNA, leaving the downstream promoter intact. Because of the placement of simple-sequence DNA, the remaining downstream promoter now becomes structurally identical to previously described VSG promoters. The downstream promoter is repetitive in the genome, since it is present at several different expression sites. Restriction fragment length polymorphism mapping allows grouping of the expression sites into two families, those with and those without an upstream transcription unit, and the DNA rearrangement events convert the expression sites from one type to the other. Deletion of the upstream transcription unit also leads to the loss of several steady-state RNAs. The findings may indicate a role for promoter-associated DNA rearrangement events, and/or interactions between tandemly arranged promoters, in expression site transcriptional control.

scholarly journals Characterization of VSG gene expression site promoters and promoter-associated DNA rearrangement events.

1991 ◽  
Vol 11 (5) ◽  
pp. 2467-2480 ◽  
Author(s):  
K Gottesdiener ◽  
H M Chung ◽  
S D Brown ◽  
M G Lee ◽  
L H Van der Ploeg
Keyword(s):  
Transcriptional Control ◽  
Transcription Unit ◽  
Surface Glycoprotein ◽  
Dna Rearrangement ◽  
Cell Surface Glycoprotein ◽  
Polycistronic Transcription ◽  
Variant Cell ◽  
Expression Site ◽  
Simple Sequence

The expressed variant cell surface glycoprotein (VSG) gene of Trypanosoma brucei is located at the 3' end of a large, telomeric, polycistronic transcription unit or expression site. We show that the region 45 kb upstream of the VSG gene, in the expression site on a 1.5-Mb chromosome, contains at least two promoters that are arranged in tandem, directing the transcription of the expression site. DNA rearrangement events occur specifically, at inactivation of the expression site, and these events delete the most upstream transcribed region and replace it with a large array of simple-sequence DNA, leaving the downstream promoter intact. Because of the placement of simple-sequence DNA, the remaining downstream promoter now becomes structurally identical to previously described VSG promoters. The downstream promoter is repetitive in the genome, since it is present at several different expression sites. Restriction fragment length polymorphism mapping allows grouping of the expression sites into two families, those with and those without an upstream transcription unit, and the DNA rearrangement events convert the expression sites from one type to the other. Deletion of the upstream transcription unit also leads to the loss of several steady-state RNAs. The findings may indicate a role for promoter-associated DNA rearrangement events, and/or interactions between tandemly arranged promoters, in expression site transcriptional control.

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