A sirtuin in the African trypanosome is involved in both DNA repair and telomeric gene silencing but is not required for antigenic variation.
Silent information regulator 2 (Sir2)-related proteins or sirtuins function as NAD(+)-dependent deacetylases or ADP ribosylases that target a range of substrates, thereby influencing chromatin structure and a diverse range of other biological functions. Genes encoding three Sir2-related proteins (SIR2rp1-3) have been identified in the parasitic trypanosomatids, early branching protozoa with no previously reported transcriptional silencing machinery. Here we show that, in the mammalian-infective bloodstream-stage of the African trypanosome, Trypanosoma brucei, SIR2rp1 localizes to the nucleus while SIR2rp2 and SIR2rp3 are both mitochondrial proteins. The nuclear protein, SIR2rp1, controls DNA repair and repression of RNA polymerase I-mediated expression immediately adjacent to telomeres. Antigenic variation, however, which involves the silencing and Pol I-mediated transcriptional switching of subtelomeric variant surface glycoprotein genes, continues to operate independent of SIR2rp1.
Alsford
Sam
S
London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK.
Kawahara
Taemi
T
Isamah
Cyril
C
Horn
David
D
D000595:Amino Acid Sequence; D000818:Animals; D000940:Antigenic Variation; D004260:DNA Repair; D020868:Gene Silencing; D008969:Molecular Sequence Data; D010802:Phylogeny; D015800:Protozoan Proteins / Q000378:metabolism*; D037761:Sirtuins / Q000378:metabolism*; D016615:Telomere; D014346:Trypanosoma brucei brucei / Q000235:genetics* / Q000378:metabolism
D015800:Protozoan Proteins; D037761:Sirtuins