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Mol. Cell. Biol., Mar 1996, 1220-1230, Vol 16, No. 3
MG Lee
To study of structure of RNA polymerase (pol) II transcription units a nd
the influence of temperature on the regulation of gene expression in
Trypanosoma brucei, and hsp70 intergenic region promoter was characterized.
In T. brucei, the hsp70 locus contains, from 5' to 3', a cognate
hsp70-related gene (gene 1) which is separated by about 6 kb of DNA from a
cluster of five identical hsp70 genes (genes 2 to 6). Transcription
proceeds on the entire 23-kb locus, and polycistronic transcription occurs
in hsp70 genes 2 to 6. Transcription of hsp70 genes 2 to 6 is only
moderately sensitive to UV irradiation, indicating that it cannot be driven
by a single far-upstream promoter, which suggests that promoters could be
located in the region close to the hsp70 coding region. Transient
transformations demonstrated that sequences located upstream of hsp70 gene
2 and in the intergenic region between hsp70 genes 2 and 3 are able to
direct transcription of the reporter gene, the chloramphenicol
acetyltransferase (CAT) gene. The plasmid DNA driven by the hsp70
intergenic region promoter gave CAT activity approximately 85-fold above to
background level. This is equivalent to approximately 1% of that derived
from a CAT plasmid driven by the procyclic acidic repetitive protein gene
promoter, which is controlled by RNA pol I. The hsp70 intergenic region
promoter can drive alpha-amanitin-sensitive transcription at an internal
position of the chromosome as well as an episome, suggesting that it is
controlled by RNA pol II. However, this hsp70 intergenic region promoter,
along with the 3' splice site and the 5' untranslated region of the hsp70
genes that controls the transcription of the reporter gene, cannot up-
regulate the expression of the reporter gene during heat shock. This result
is consistent with the previous observation that expression of the hsp70
genes in T. brucei is mainly controlled at the posttranscriptional level.
Copyright © 1996, American Society for Microbiology
An RNA polymerase II promoter in the hsp70 locus of Trypanosoma brucei
Department of Pathology, New York University Medical Center 10016, USA.
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