title: Ablation of RNA interference and retrotransposons accompany acquisition and evolution of transposases to heterochromatin protein CENPB.
abstract: Inactivation of retrotransposons is accompanied by the emergence of centromere-binding protein-B (CENPB) inSchizosaccharomyces, as well as in metazoans. The RNA interference (RNAi)-induced transcriptional silencing (RITS) complex, comprising chromodomain protein-1 (Chp1), Tas3 (protein with unknown function), and Argonaute (Ago1), plays an important role in RNAi-mediated heterochromatinization. We find that whereas the Ago1 subunit of the RITS complex is highly conserved, Tas3 is lost and Chp1 is truncated inSchizosaccharomyces cryophilusandSchizosaccharomyces octosporusWe show that truncated Chp1 loses the property of heterochromatin localization and silencing when transformed inSchizosaccharomyces pombeFurthermore, multiple copies of CENPB, related toTc1/mariner and Tc5transposons, occur in allSchizosaccharomycesspecies, as well as in humans, but with loss of transposase function (exceptSchizosaccharomyces japonicus). We propose that acquisition ofTc1/mariner and Tc5elements by horizontal transfer inS. pombe(and humans) is accompanied by alteration of their function from a transposase/endonuclease to a heterochromatin protein, designed to suppress transposon expression and recombination. The resulting redundancy of RITS may have eased the selection pressure, resulting in progressive loss or truncation oftas3andchp1genes inS. octosporusandS. cryophilusand triggered similar evolutionary dynamics in the metazoan orthologues.
authors.affiliation: Department of Anesthesiology, Miller School of Medicine, University of Miami, Miami, FL 33136.
authors.forename: Udita
authors.initials: U
authors.lastname: Upadhyay
authors.affiliation: Yeast Epigenetic Regulation Laboratory, Council of Scientific and Industrial Research, Chandigarh 160036, India.
authors.forename: Suchita
authors.initials: S
authors.lastname: Srivastava
authors.affiliation: Department of Medicine and Biology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215.
authors.forename: Indu
authors.initials: I
authors.lastname: Khatri
authors.affiliation: Department of Pharmacology, Case Western Reserve University, Cleveland, OH 44106.
authors.forename: Jagpreet Singh
authors.initials: JS
authors.lastname: Nanda
authors.affiliation: Protein Evolution Laboratory, Council of Scientific and Industrial Research, Chandigarh 160036, India.
authors.forename: Srikrishna
authors.initials: S
authors.lastname: Subramanian
authors.affiliation: Microbial Type Culture Collection, Institute of Microbial Technology, Council of Scientific and Industrial Research, Chandigarh 160036, India.
authors.forename: Amit
authors.initials: A
authors.lastname: Arora
authors.affiliation: Yeast Epigenetic Regulation Laboratory, Council of Scientific and Industrial Research, Chandigarh 160036, India jag@imtech.res.in.
authors.forename: Jagmohan
authors.initials: J
authors.lastname: Singh
mesh_terms: D060565:Argonaute Proteins / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D002503:Centromere / Q000378:metabolism; D051936:Centromere Protein B / Q000378:metabolism*; D047369:Chromatin Immunoprecipitation; D019143:Evolution, Molecular; D006570:Heterochromatin / Q000378:metabolism*; D034622:RNA Interference; D012331:RNA, Fungal / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D018626:Retroelements / Q000235:genetics*; D012568:Schizosaccharomyces / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism; D019895:Transposases / Q000235:genetics* / Q000378:metabolism*
chemical_list: C481643:Ago1 protein, S pombe; D060565:Argonaute Proteins; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D051936:Centromere Protein B; C115018:Chp1 protein, S pombe; D006570:Heterochromatin; D012331:RNA, Fungal; D034741:RNA, Small Interfering; D018626:Retroelements; D029702:Schizosaccharomyces pombe Proteins; C499720:Tas3 protein, S pombe; D019895:Transposases