Transcription of the procyclic acidic repetitive protein genes of Trypanosoma brucei.

Abstract

The procyclic acidic repetitive protein (parp) genes of Trypanosoma brucei encode a small family of abundant surface proteins whose expression is restricted to the procycfic form of the parasite. They are found at two unlinked loci, parpA and parpB; transcription of both loci is developmentally regulated. The region of homology upstream of the A and B parp genes is only 640 base pairs long and may contain sequences responsible for transcriptional initiation and regulation. Transcription upstream of this putative promoter region is not developmentally regulated and is much less active than that of the parp genes; the polymerase responsible is inhibited by a-amanitin, whereas that transcribing the parp genes is not. Transcription of the parp genes is strongly stimulated by low levels of UV irradiation. The putative parp promoter, when placed upstream of the chloramphenicol acetyltransferase gene, is sufficient to cause production of chloramphenicol acetyltransferase in a T. brucei DNA transformation assay. Taken together, these results suggest that a promoter for an a-amanitin-resistant RNA polymerase lies less than 600 nucleotides upstream of the parp genes.

Coupling of poly(A) site selection and trans-splicing in Leishmania.

“…In total, these data show that the primary determinant affecting the site of poly(A) addition in Leishmania is the presence and positioning of a functional splice acceptor immediately downstream. This may explain why it is often unnecessary to include a 3' poly(A) site for expression in trypanosomatids (Laban and Wirth 1989;Clayton et al 1990;Rudenko et al 1990;Zomerdijk et al 1990;Bellofatto et al 1991), as the obligate inclusion of a splice acceptor would specify simultaneously 3'-end formation. In contrast, omission of the AAUAAA/GU-rich polyadenylation signal from analogous mammalian constructs results in the formation of nonfunctional "runaround" RNAs (Colmelly and Manley 1988).…”

“…These premRNAs can encode genes that are expressed (1) at similar levels, such as tubulins or calmodulins (Sather and Agabian 1985;Imboden et al 1986;Landfear et al 1986;Tschudi and Ullu 1988), (2} at very different levels, such as the variant surface glycoprotein (VSG) expression sites (Cully et al 1985;Kooter et al 1987;Shea and Van der Ploeg 1988;Aline et al 1989;Pays et al 1989), or (3) at levels varying greatly during development, such as the aldolase or Lm 16 loci (Vijayasarathy et al 1990;Flinn and Smith 1992). Consequently, the mechanism and regulation of mRNA processing reactions occurring in the intergenic regions of the pre-mRNAs is a primary determinant of regulated gene expression.…”

In vivo import of firefly luciferase into the glycosomes of Trypanosoma brucei and mutational analysis of the C-terminal targeting signal.

“…Transient transformation of trypanosomes with foreign DNA (Clayton et al, 1990;Rudenko et al, 1990;Jefferies et al, 1991) or from a T. brucei receptor RNA gene (Rudenko et al, 1991). The neo gene could also be stably expressed without the addition of a promoter element by inserting it into an actively transcribed region, such as the tubulin or calmodulin locus (ten Asbroek et al, 1990;Eid and Sollner-Webb, 1991).…”

Procyclic acidic repetitive protein (PARP) genes located in an unusually small alpha-amanitin-resistant transcription unit: PARP promoter activity assayed by transient DNA transfection of Trypanosoma brucei.

“…The bloodstream form is sheathed by a dense variant cell surface glycoprotein (VSG) coat which is lost upon differentiation into the procyclic form. The procyclic trypanosome is characterized by an abundant cell surface protein, the procyclic acidic repetitive protein (PARP) or procyclin (7,(27)(28)(29)(33)(34)(35). The Transcription of many protein-coding genes in trypanosomes and related species is believed to be polycistronic, generating large precursor RNAs (pre-mRNAs) containing multiple protein-coding genes.…”