title: Locus-specific control of DNA resection and suppression of subtelomeric VSG recombination by HAT3 in the African trypanosome.
abstract: The African trypanosome, Trypanosoma brucei, is a parasitic protozoan that achieves antigenic variation through DNA-repair processes involving Variant Surface Glycoprotein (VSG) gene rearrangements at subtelomeres. Subtelomeric suppression of DNA repair operates in eukaryotes but little is known about these controls in trypanosomes. Here, we identify a trypanosome histone acetyltransferase (HAT3) and a deacetylase (SIR2rp1) required for efficient RAD51-dependent homologous recombination. HAT3 and SIR2rp1 were required for RAD51-focus assembly and disassembly, respectively, at a chromosome-internal locus and a synthetic defect indicated distinct contributions to DNA repair. Although HAT3 promoted chromosome-internal recombination, it suppressed subtelomeric VSG recombination, and these locus-specific effects were mediated through differential production of ssDNA by DNA resection; HAT3 promoted chromosome-internal resection but suppressed subtelomeric resection. Consistent with the resection defect, HAT3 was specifically required for the G2-checkpoint response at a chromosome-internal locus. HAT3 also promoted resection at a second chromosome-internal locus comprising tandem-duplicated genes. We conclude that HAT3 and SIR2rp1 can facilitate temporally distinct steps in DNA repair. HAT3 promotes ssDNA formation and recombination at chromosome-internal sites but has the opposite effect at a subtelomeric VSG. These locus-specific controls reveal compartmentalization of the T. brucei genome in terms of the DNA-damage response and suppression of antigenic variation by HAT3.
authors.affiliation: Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK.
authors.forename: Lucy
authors.initials: L
authors.lastname: Glover
authors.affiliation: Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK d.horn@dundee.ac.uk.
authors.forename: David
authors.initials: D
authors.lastname: Horn
mesh_terms: D000940:Antigenic Variation / Q000235:genetics*; D053903:DNA Breaks, Double-Stranded; D004277:DNA, Single-Stranded / Q000378:metabolism; D059565:G2 Phase Cell Cycle Checkpoints / Q000235:genetics; D056426:Genetic Loci; D056545:Group III Histone Deacetylases / Q000235:genetics / Q000502:physiology*; D051548:Histone Acetyltransferases / Q000235:genetics / Q000502:physiology*; D015800:Protozoan Proteins / Q000235:genetics / Q000502:physiology*; D051135:Rad51 Recombinase / Q000378:metabolism; D059767:Recombinational DNA Repair; D016615:Telomere; D014346:Trypanosoma brucei brucei / Q000201:enzymology / Q000235:genetics* / Q000276:immunology; D014643:Variant Surface Glycoproteins, Trypanosoma / Q000235:genetics*
chemical_list: D004277:DNA, Single-Stranded; D015800:Protozoan Proteins; D014643:Variant Surface Glycoproteins, Trypanosoma; D051548:Histone Acetyltransferases; D051135:Rad51 Recombinase; D056545:Group III Histone Deacetylases