TY  - JOUR
A1  - Reynolds, David
A1  - Cliffe, Laura
A1  - Förstner, Konrad U.
A1  - Hon, Chung-Chau
A1  - Siegel, T. Nicolai
A1  - Sabatini, Robert
T1  - Regulation of transcription termination by glucosylated hydroxymethyluracil, base J, in Leishmania major and Trypanosoma brucei
JF  - Nucleic Acids Research
N2  - Base J, beta-d-glucosyl-hydroxymethyluracil, is an epigenetic modification of thymine in the nuclear DNA of flagellated protozoa of the order Kinetoplastida. J is enriched at sites involved in RNA polymerase ( RNAP) II initiation and termination. Reduction of J in Leishmania tarentolae via growth in BrdU resulted in cell death and indicated a role of J in the regulation of RNAP II termination. To further explore J function in RNAP II termination among kinetoplastids and avoid indirect effects associated with BrdU toxicity and genetic deletions, we inhibited J synthesis in Leishmania major and Trypanosoma brucei using DMOG. Reduction of J in L. major resulted in genome-wide defects in transcription termination at the end of polycistronic gene clusters and the generation of antisense RNAs, without cell death. In contrast, loss of J in T. brucei did not lead to genome-wide termination defects; however, the loss of J at specific sites within polycistronic gene clusters led to altered transcription termination and increased expression of downstream genes. Thus, J regulation of RNAP II transcription termination genome-wide is restricted to Leishmania spp., while in T. brucei it regulates termination and gene expression at specific sites within polycistronic gene clusters.
KW  - RNA-polymerase-II
KW  - variant surface glycoprotein
KW  - SWI2/SNF2-like protein
KW  - messenger RNA
KW  - polycistronic transcription
KW  - DNA glycosation
KW  - hela cells
KW  - gene expression
KW  - genome
KW  - 5-bromodeoxyuridine
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-117863
VL  - 42
IS  - 15
ER  - 
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  -