TY  - JOUR
A1  - Reynolds, David
A1  - Hofmeister, Brigitte T.
A1  - Cliffe, Laura
A1  - Alabady, Magdy
A1  - Siegel, T. Nicolai
A1  - Schmitz, Robert J.
A1  - Sabatini, Robert
T1  - Histone H3 Variant Regulates RNA Polymerase II Transcription Termination and Dual Strand Transcription of siRNA Loci in Trypanosoma brucei
JF  - PLoS Genetics
N2  - Base J, β-D-glucosyl-hydroxymethyluracil, is a chromatin modification of thymine in the nuclear DNA of flagellated protozoa of the order Kinetoplastida. In Trypanosoma brucei, J is enriched, along with histone H3 variant (H3.V), at sites involved in RNA Polymerase (RNAP) II termination and telomeric sites involved in regulating variant surface glycoprotein gene (VSG) transcription by RNAP I. Reduction of J in T. brucei indicated a role of J in the regulation of RNAP II termination, where the loss of J at specific sites within polycistronic gene clusters led to read-through transcription and increased expression of downstream genes. We now demonstrate that the loss of H3.V leads to similar defects in RNAP II termination within gene clusters and increased expression of downstream genes. Gene derepression is intensified upon the subsequent loss of J in the H3.V knockout. mRNA-seq indicates gene derepression includes VSG genes within the silent RNAP I transcribed telomeric gene clusters, suggesting an important role for H3.V in telomeric gene repression and antigenic variation. Furthermore, the loss of H3.V at regions of overlapping transcription at the end of convergent gene clusters leads to increased nascent RNA and siRNA production. Our results suggest base J and H3.V can act independently as well as synergistically to regulate transcription termination and expression of coding and non-coding RNAs in T. brucei, depending on chromatin context (and transcribing polymerase). As such these studies provide the first direct evidence for histone H3.V negatively influencing transcription elongation to promote termination.
KW  - RNA polymerase
KW  - Trypanosoma brucei
KW  - histone H3
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-166738
VL  - 12
IS  - 1
ER  - 
TY  - JOUR
A1  - Reynolds, David L.
A1  - Hofmeister, Brigitte T.
A1  - Cliffe, Laura
A1  - Siegel, T. Nicolai
A1  - Andersson, Britta A.
A1  - Beverley, Stephen M.
A1  - Schmitz, Robert J.
A1  - Sabatini, Robert
T1  - Base J represses genes at the end of polycistronic gene clusters in Leishmania major by promoting RNAP II termination
JF  - Molecular Microbiology
N2  - The genomes of kinetoplastids are organized into polycistronic gene clusters that are flanked by the modified DNA base J. Previous work has established a role of base J in promoting RNA polymerase II termination in Leishmania spp. where the loss of J leads to termination defects and transcription into adjacent gene clusters. It remains unclear whether these termination defects affect gene expression and whether read through transcription is detrimental to cell growth, thus explaining the essential nature of J. We now demonstrate that reduction of base J at specific sites within polycistronic gene clusters in L. major leads to read through transcription and increased expression of downstream genes in the cluster. Interestingly, subsequent transcription into the opposing polycistronic gene cluster does not lead to downregulation of sense mRNAs. These findings indicate a conserved role for J regulating transcription termination and expression of genes within polycistronic gene clusters in trypanosomatids. In contrast to the expectations often attributed to opposing transcription, the essential nature of J in Leishmania spp. is related to its role in gene repression rather than preventing transcriptional interference resulting from read through and dual strand transcription.
KW  - Trypanosoma-brucei
KW  - Transcription initiation
KW  - Messenger RNA
KW  - DNA
KW  - Genome
KW  - Cruzi
KW  - Hydroxymethyluracil
KW  - Expression
KW  - Parasite
KW  - Glucosyltransferase
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-187727
VL  - 101
IS  - 4
ER  -