title: Retrotransposon-mediated restoration of Chlorella telomeres: accumulation of Zepp retrotransposons at termini of newly formed minichromosomes.
abstract: To elucidate the contribution of LINE-like retrotransposon Zepp elements to the formation and maintenance of chromosomal telomeres, newly formed minichromosomes in irradiated Chlorella vulgaris cells were isolated and structurally characterized. A minichromosome (miniV4) of approximately 700 kb in size contained a Zepp cluster taking the place of the telomeric repeats on one terminus, whereas the other end of this chromosome consisted of canonical telomeric repeats. The Zepp copies in this cluster were in a tandem array with their poly(A) tails towards the centromere. Another minichromosome Y32 ( approximately 400 kb in size) was shown to have several copies of Zepp elements on both termini. On the right arm terminus, two copies of Zepp were found in a tandem array with poly(A) tracts facing towards the chromosomal end. The poly(A) tail and the 3'-end of approximately 400 bp of the distal copy were replaced by the telomeric repeats. On the 5'-side of the proximal copy was another Zepp element in the reverse orientation. These newly formed telomeric structures are very similar to those previously found in the left arm of chromosome I and the terminus of an unidentified chromosome and support the model of Zepp-mediated restoration and maintenance of Chlorella telomeres.
authors.affiliation: Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530, Japan.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Yuhki
authors.initials: Y
authors.lastname: Fujimoto
authors.forename: Ryota
authors.initials: R
authors.lastname: Arai
authors.forename: Makoto
authors.initials: M
authors.lastname: Fujie
authors.forename: Shoji
authors.initials: S
authors.lastname: Usami
authors.forename: Takashi
authors.initials: T
authors.lastname: Yamada
mesh_terms: D001483:Base Sequence; D002708:Chlorella / Q000235:genetics* / Q000528:radiation effects; D002875:Chromosomes / Q000528:radiation effects; D008969:Molecular Sequence Data; D018626:Retroelements; D017422:Sequence Analysis, DNA; D016615:Telomere / Q000737:chemistry*
chemical_list: D018626:Retroelements