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Nucleic Acids Res ; 24(7): 1202-11, 1996 Apr 01.
Article in English | MEDLINE | ID: mdl-8614620

ABSTRACT

African trypanosomes are extracellular protozoan parasites that are transmitted from one mammalian host to the next by tsetse flies. Bloodstream forms express variant surface glycoprotein (VSG); the tsetse fly (procyclic) forms express instead the procyclic acidic repetitive protein (PARP). PARP mRNA is abundant in procyclic forms and almost undetectable in blood-stream forms. Post-transcriptional mechanisms are mainly responsible for PARP mRNA regulation but results of nuclear run-on experiments suggested that transcription might also be regulated. We measured the activity of genomically-integrated PARP, VSG and rRNA promoters in permanently-transformed blood-stream and procyclic form trypanosomes, using reporter gene constructs that showed no post-transcriptional regulation. When the constructs were integrated in the rRNA non-transcribed spacer, the ribosomal RNA and VSG promoters were not developmentally regulated, but integration at the PARP locus reduced rRNA promoter activity in bloodstream forms. PARP promoter activity was 5-fold down-regulated in bloodstream forms when integrated at either site. Regulation was probably at the level of transcriptional initiation, but elongation through plasmid vector sequences was also reduced.


Subject(s)
Gene Expression Regulation, Developmental , Membrane Glycoproteins/genetics , Promoter Regions, Genetic , Protozoan Proteins , Trypanosoma brucei brucei/genetics , Animals , Base Sequence , DNA Primers/chemistry , Molecular Sequence Data , RNA, Ribosomal/genetics , Transcription, Genetic , Tubulin/genetics
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