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Well-positioned nucleosomes punctuate polycistronic Pol II transcription units and flank silent VSG gene arrays in Trypanosoma brucei

ABSTRACT: Trypanosoma brucei, a member of the Excavates supergroup, falls in an evolutionarily ancient branch of eukaryotes. We have mapped nucleosome positions in T. brucei and identified a map that differs from that of other eukaryotes in several important ways. Unlike in other eukaryotes, the RNA polymerase II initiation regions in T. brucei do not exhibit pronounced nucleosome depletion, and show little evidence for defined -1 and +1 nucleosomes. In contrast, a well-positioned nucleosome is present directly on the splice acceptor sites within the polycistronic transcription units. The RNA polyadenylation sites were depleted of nucleosomes, with a single well-positioned nucleosome present immediately downstream of the predicted sites. The regions flanking the silent Variant Surface Glycoprotein (VSG) gene arrays showed extensive arrays of well-positioned nucleosomes, which may act to repress cryptic transcription initiation. The silent VSG genes themselves exhibited a less regular nucleosomal pattern in both bloodstream and procyclic form trypanosomes. The DNA replication origins, when present within arrays of silent VSG genes, displayed a defined nucleosomal organization compared with replication origins in other chromosomal core regions. Our results indicate that some organizational features of chromatin are evolutionarily ancient, and may already have been present in the last eukaryotic common ancestor.

ORGANISM(S): Trypanosoma brucei

PROVIDER: GSE90593 | GEO | 2017/03/13

SECONDARY ACCESSION(S): PRJNA355131

REPOSITORIES: GEO

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Trypanosoma brucei

Project description:Well-positioned nucleosomes punctuate polycistronic Pol II transcription units and flank silent VSG gene arrays in Trypanosoma brucei

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