Open AccessCpG Methylation of DNA Restricts Prereplication Complex Assembly in Xenopus Egg Extracts
Author(s) -
Kevin J. Harvey,
John W. Newport
Publication year - 2003
Publication title -
molecular and cellular biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.14
H-Index - 327
eISSN - 1067-8824
pISSN - 0270-7306
DOI - 10.1128/mcb.23.19.6769-6779.2003
Subject(s) - biology , xenopus , dna replication , origin recognition complex , cpg site , dna , microbiology and biotechnology , dna methylation , control of chromosome duplication , dna replication factor cdt1 , licensing factor , eukaryotic dna replication , genetics , gene , gene expression
In a Xenopus egg replication system, the origin recognition complex (ORC) does not bind to CpG methylated DNA and DNA replication is inhibited. Insertion of low density CpG DNA of at least 1.2 kb into methylated plasmids rescues both replication and ORC binding. Using this pseudo-origin, we find that ORC binding is restricted to low-CpG-density DNA; however, MCM is loaded onto both weakly and highly methylated DNA and occupies at least approximately 2 kb of DNA. Replication initiates coincident with MCM, and even the most distally bound MCM is associated with sites of replication initiation. These results suggest that in metazoans MCM is loaded onto and initiates replication over a large region distant from ORC.