Genome-wide Analysis Reveals Extensive Functional Interaction between DNA Replication Initiation and Transcription in the Genome of Trypanosoma brucei

• DOI: 10.1016/j.celrep.2012.06.007
• Publication Date: 2012-07-15T00:02:35Z
• Authors: Calvin Tiengwe; Lucio Marcello; Helen Farr; Nicholas Dickens; Steven Kelly; Michal Swiderski; Diane Vaughan; Keith Gull; J. David Barry; Stephen D. Bell; Richard McCulloch
• Keywords: Resource; DNA Replication; 0301 basic medicine; Binding Sites; Transcription, Genetic; QH301-705.5; Trypanosoma brucei brucei; Origin Recognition Complex; Epistasis, Genetic; Replication Origin; Sequence Analysis, DNA; Models, Biological; 03 medical and health sciences; Gene Expression Regulation; Biology (General); Genome, Protozoan

Identification of replication initiation sites, termed origins, is a crucial step in understanding genome transmission in any organism. Transcription of the Trypanosoma brucei genome is highly unusual, with each chromosome comprising a few discrete transcription units. To understand how DNA replication occurs in the context of such organization, we have performed genome-wide mapping of the binding sites of the replication initiator ORC1/CDC6 and have identified replication origins, revealing that both localize to the boundaries of the transcription units. A remarkably small number of active origins is seen, whose spacing is greater than in any other eukaryote. We show that replication and transcription in T. brucei have a profound functional overlap, as reducing ORC1/CDC6 levels leads to genome-wide increases in mRNA levels arising from the boundaries of the transcription units. In addition, ORC1/CDC6 loss causes derepression of silent Variant Surface Glycoprotein genes, which are critical for host immune evasion.