Understanding the DNA replication programmes of the African trypanosome and Leishmania

To ensure accurate genome transmission, eukaryotes employ regulated DNA replication programmes where DNA synthesis initiates in S-phase at multiple defined origins. Despite considerable understanding, many questions remain: what dictates origin location; how (in)flexible is a cell’s DNA replication programme; and when do cells employ origin-independent DNA replication? This application seeks to examine the DNA replication programme of two eukaryotic parasites, Trypanosoma brucei and Leishmania major, where DNA replication flexibility appears central to their biology: 1. T. brucei chromosomes are compartmentalised into a stable, highly transcribed core and unstable, transcriptionally silent subtelomeres, with dramatically differing levels of mapped origins. This application will ask how and why replication compartmentalisation occurs. 2. T. brucei survival relies on recombination of subtelomeric genes encoding Variant Surface Glycoproteins into telomere-adjacent transcription units, one of which is replicated uniquely early in S-phase. This application will ask how such targeted DNA replication occurs and if it drives recombination. 3. L. major appears to have evolved genome-wide DNA replication programme re-wiring: just one origin is activated in each chromosome during S-phase; and subtelomeric DNA replication occurs outside S-phase. This application will ask if L. major has de-emphasized conventional origin-derived replication, allowing more flexible DNA replication to promote genome plasticity.