Interaction between the origin recognition complex and the replication licensing system in Xenopus.
The origin recognition complex (ORC) binds to origins of replication in budding yeast. We have cloned a Xenopus homolog of the largest ORC polypeptide (XORC1). Immunodepletion of XOrc1 from Xenopus egg extracts blocks the initiation of DNA replication. We have purified Xenopus ORC, consisting of a protein complex similar to yeast ORC. In Xenopus egg extracts, ORC associates with chromatin throughout G1 and S phases. RLF-M, a component of the replication licensing system, also associates with chromatin early in the cell cycle but dissociates during S phase. We show that the assembly of RLF-M onto chromatin is dependent on the presence of chromatin-bound ORC, leading to sequential assembly of initiation proteins onto replication origins during the cell cycle.
Rowles
A
A
Imperial Cancer Research Fund, Clare Hall Laboratories, Herts, United Kingdom.
Chong
J P
JP
Brown
L
L
Howell
M
M
Evan
G I
GI
Blow
J J
JJ
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002453:Cell Cycle; D002474:Cell-Free System; D002843:Chromatin / Q000378:metabolism / Q000648:ultrastructure; D003001:Cloning, Molecular; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000502:physiology*; D006801:Humans; D007158:Immunologic Techniques; D008297:Male; D008969:Molecular Sequence Data; D009865:Oocytes; D051738:Origin Recognition Complex; D016415:Sequence Alignment; D013094:Spermatozoa; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000235:genetics*
D002843:Chromatin; D004268:DNA-Binding Proteins; D051738:Origin Recognition Complex; C102178:XOrc1 protein, Xenopus; D029867:Xenopus Proteins