The PARP promoter of Trypanosoma brucei is developmentally regulated in a chromosomal context.
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.
Biebinger
S
S
Zentrum für Molekulare Biologie, Universität Heidelberg, Germany.
Rettenmaier
S
S
Flaspohler
J
J
Hartmann
C
C
Peña-Diaz
J
J
Wirtz
L E
LE
Hotz
H R
HR
Barry
J D
JD
Clayton
C
C
D000818:Animals; D001483:Base Sequence; D017931:DNA Primers / Q000737:chemistry; D018507:Gene Expression Regulation, Developmental; D008562:Membrane Glycoproteins / Q000235:genetics*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D015800:Protozoan Proteins; D012335:RNA, Ribosomal / Q000235:genetics; D014158:Transcription, Genetic; D014346:Trypanosoma brucei brucei / Q000235:genetics*; D014404:Tubulin / Q000235:genetics
D017931:DNA Primers; D008562:Membrane Glycoproteins; D015800:Protozoan Proteins; D012335:RNA, Ribosomal; D014404:Tubulin; C053277:procyclic acidic repetitive protein, Trypanosoma