TY  - JOUR
A1  - Nguyen, Tu N.
A1  - Müller, Laura S. M.
A1  - Park, Sung Hee
A1  - Siegel, T. Nicolai
A1  - Günzl, Arthur
T1  - Promoter occupancy of the basal class I transcription factor A differs strongly between active and silent VSG expression sites in Trypanosoma brucei
JF  - Nucleic Acid Research
N2  - Monoallelic expression within a gene family is found in pathogens exhibiting antigenic variation and in mammalian olfactory neurons. Trypanosoma brucei, a lethal parasite living in the human bloodstream, expresses variant surface glycoprotein (VSG) from 1 of 15 bloodstream expression sites (BESs) by virtue of a multifunctional RNA polymerase I. The active BES is transcribed in an extranucleolar compartment termed the expression site body (ESB), whereas silent BESs, located elsewhere within the nucleus, are repressed epigenetically. The regulatory mechanisms, however, are poorly understood. Here we show that two essential subunits of the basal class I transcription factor A (CITFA) predominantly occupied the promoter of the active BES relative to that of a silent BES, a phenotype that was maintained after switching BESs in situ. In these experiments, high promoter occupancy of CITFA was coupled to high levels of both promoter-proximal RNA abundance and RNA polymerase I occupancy. Accordingly, fluorescently tagged CITFA-7 was concentrated in the nucleolus and the ESB. Because a ChIP-seq analysis found that along the entire BES, CITFA-7 is specifically enriched only at the promoter, our data strongly indicate that monoallelic BES transcription is activated by a mechanism that functions at the level of transcription initiation.
KW  - RNA-polymerase-I
KW  - blood-stream forms
KW  - acrican trypanosomes
KW  - gene expression
KW  - antigenic variation
KW  - ribosomal RNA
KW  - plasmodium falciparum
KW  - virulence genes
KW  - subunit
KW  - complex
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-117232
SN  - 1362-4962
VL  - 42
IS  - 5
ER  - 
TY  - JOUR
A1  - Gassen, Alwine
A1  - Brechtefeld, Doris
A1  - Schandry, Niklas
A1  - Arteaga-Salas, J. Manuel
A1  - Israel, Lars
A1  - Imhof, Axel
A1  - Janzen, Christian J.
T1  - DOT1A-dependent H3K76 methylation is required for replication regulation in Trypanosoma brucei
JF  - Nucleic Acids Research
N2  - Cell-cycle progression requires careful regulation to ensure accurate propagation of genetic material to the daughter cells. Although many cell-cycle regulators are evolutionarily conserved in the protozoan parasite Trypanosoma brucei, novel regulatory mechanisms seem to have evolved. Here, we analyse the function of the histone methyltransferase DOT1A during cell-cycle progression. Over-expression of DOT1A generates a population of cells with aneuploid nuclei as well as enucleated cells. Detailed analysis shows that DOT1A over-expression causes continuous replication of the nuclear DNA. In contrast, depletion of DOT1A by RNAi abolishes replication but does not prevent karyokinesis. As histone H3K76 methylation has never been associated with replication control in eukaryotes before, we have discovered a novel function of DOT1 enzymes, which might not be unique to trypanosomes.
KW  - variants
KW  - cell-cycle regulation
KW  - blood-stream forms
KW  - african trypanosomes
KW  - mammalian cells
KW  - DNA replication
KW  - DOT1
KW  - protein
KW  - transcription
KW  - cultivation
Y1  - 2012
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-131449
VL  - 40
IS  - 20
ER  -