Qi CC, Urményi T, Gottesdiener KM. Analysis of a hybrid PARP/VSG ES promoter in procyclic trypanosomes.
Mol Biochem Parasitol 1996;
77:147-59. [PMID:
8813661 DOI:
10.1016/0166-6851(96)02588-1]
[Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The parasite Trypanosoma brucei changes its variant surface glycoprotein (VSG) coat to escape the host immune system. At a chromosomal locus, we analyzed the promoter that controls expression of VSG genes, using a system developed in collaboration with Urményi and Van der Ploeg (Urményi, T.P. and Van der Ploeg, L.H.T. (1995) Nucleic Acids Res. 23,1010-1016), and showed that the variant surface glycoprotein expression site (VSG ES) promoter directed < 6% the CAT activity produced by the procyclic acidic repetitive protein (PARP) promoter at the same locus. We identified a fragment from the PARP promoter (bp -743 to -111) that contained no intrinsic promoter activity. However, when this fragment was cloned 5' to 3' upstream of the VSG ES promoter, and this hybrid PARP/VSG ES promoter was stably integrated at the RNA polymerase (Pol) II largest subunit gene locus, expression from a CAT gene cassette increased 10-fold. Nascent RNA analysis independently showed that the relative efficiency of alpha-amanitin-resistant transcription directed by the hybrid PARP/VSG ES promoter was more than 6-fold higher than that directed by the wild-type VSG ES promoter. Furthermore, using nascent RNA protection assays, we mapped the transcription start site of the hybrid PARP/VSG ES promoter to the same initiation site as that of the wild-type VSG ES promoter. Finally, we evaluated the functional activity of the hybrid PARP/VSG ES mutant promoter at the dominant VSG gene expression site on the 1.5-Mb chromosome. At this locus, as well, the hybrid PARP/VSG ES promoter directed almost 3-times as much CAT activity as that of the wild-type VSG ES promoter.
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