title: Xenopus laevis Ctc1-Stn1-Ten1 (xCST) protein complex is involved in priming DNA synthesis on single-stranded DNA template in Xenopus egg extract.
abstract: The Ctc1-Stn1-Ten1 (CST) complex is an RPA (replication protein A)-like protein complex that binds to single-stranded (ss) DNA. It localizes at telomeres and is involved in telomere end protection in mammals and plants. It is also known to stimulate DNA polymerase α-primase in vitro. However, it is not known how CST accomplishes these functions in vivo. Here, we report the identification and characterization of Xenopus laevis CST complex (xCST). xCST showed ssDNA binding activity with moderate preference for G (guanine)-rich sequences. xStn1-immunodepleted Xenopus egg extracts supported chromosomal DNA replication in in vitro reconstituted sperm nuclei, suggesting that xCST is not a general replication factor. However, the immunodepletion or neutralization of xStn1 compromised DNA synthesis on ssDNA template. Because primed ssDNA template was replicated in xStn1-immunodepleted extracts as efficiently as in control ones, we conclude that xCST is involved in the priming step on ssDNA template. These results are consistent with the current model that CST is involved in telomeric C-strand synthesis through the regulation of DNA polymerase α-primase.
authors.affiliation: Laboratory of Cell Cycle Regulation, Department of Gene Mechanisms, Graduate School of Biostudies, Kyoto University, Yoshida-Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Hidenori
authors.initials: H
authors.lastname: Nakaoka
authors.affiliation: Laboratory of Cell Cycle Regulation, Department of Gene Mechanisms, Graduate School of Biostudies, Kyoto University, Yoshida-Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Atsuya
authors.initials: A
authors.lastname: Nishiyama
authors.affiliation: Laboratory of Cell Cycle Regulation, Department of Gene Mechanisms, Graduate School of Biostudies, Kyoto University, Yoshida-Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Motoki
authors.initials: M
authors.lastname: Saito
authors.affiliation: Laboratory of Cell Cycle Regulation, Department of Gene Mechanisms, Graduate School of Biostudies, Kyoto University, Yoshida-Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan. Electronic address: fishikaw@lif.kyoto-u.ac.jp.
authors.forename: Fuyuki
authors.initials: F
authors.lastname: Ishikawa
mesh_terms: D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D002843:Chromatin / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D004261:DNA Replication; D004277:DNA, Single-Stranded / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D020862:GC Rich Sequence / Q000235:genetics; D006801:Humans; D008297:Male; D010063:Ovum / Q000378:metabolism*; D021381:Protein Transport; D013094:Spermatozoa / Q000166:cytology / Q000378:metabolism; D013379:Substrate Specificity; D016615:Telomere / Q000235:genetics / Q000378:metabolism; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis / Q000235:genetics* / Q000378:metabolism*
chemical_list: D002843:Chromatin; D004277:DNA, Single-Stranded; D029867:Xenopus Proteins
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