title: Plasmodium falciparum origin recognition complex subunit 1 (PfOrc1) functionally complements Δsir3 mutant of Saccharomyces cerevisiae.
abstract: Telomere position effect efficiently controls silencing of subtelomeric var genes, which are involved in antigenic variation in human malaria parasite Plasmodium falciparum. Although, PfOrc1 has been found to be associated with PfSir2 in the silencing complex, its function in telomere silencing remained uncertain especially due to an apparent lack of BAH domain at its amino-terminal region. Here we report that PfOrc1 possesses a Sir3/Orc1 like silencing activity. Using yeast as a surrogate organism we have shown that PfOrc1 could complement yeast Sir3 activity during telomere silencing in a Sir2 dependent manner. By constructing a series of chimera between PfOrc1 and ScSir3 we have observed that the amino-terminal domain of PfOrc1 harbors silencing activity similar to that present in the amino-terminal domain of ScSir3. We further generated several amino-terminal deletion mutants to dissect out such silencing activity and found that the first seventy amino acids at the amino-terminal domain are dispensable for its activity. Thus our results strongly supports that PfOrc1 may have a role in telomere silencing in this parasite. This finding will help to decipher the mechanism of telomere position effect in P. falciparum.
authors.affiliation: Department of Biochemistry, School of Life Sciences, University of Hyderabad, Gachibowli, Hyderabad 500046, Andhra Pradesh, India.
authors.forename: Shalu M
authors.initials: SM
authors.lastname: Varunan
authors.forename: Jaishree
authors.initials: J
authors.lastname: Tripathi
authors.forename: Sunanda
authors.initials: S
authors.lastname: Bhattacharyya
authors.forename: Tanvi
authors.initials: T
authors.lastname: Suhane
authors.forename: Mrinal Kanti
authors.initials: MK
authors.lastname: Bhattacharyya
mesh_terms: D005816:Genetic Complementation Test; D051738:Origin Recognition Complex / Q000235:genetics* / Q000378:metabolism; D010963:Plasmodium falciparum / Q000201:enzymology* / Q000235:genetics; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae / Q000172:deficiency* / Q000235:genetics; D016615:Telomere / Q000378:metabolism
chemical_list: D051738:Origin Recognition Complex; D021122:Protein Subunits; C084122:SIR3 protein, S cerevisiae; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae
keywords: Orc1; Plasmodium falciparum; Saccharomyces cerevisiae; Sir3; Telomere position effect; var gene silencing