Genome Res. 17:865-876, 2007
©2007 by Cold Spring Harbor Laboratory Press; ISSN 1088-9051/07 $5.00
OPEN ACCESS ARTICLE
Letter
Pan-S replication patterns and chromosomal domains defined by genome-tiling arrays of ENCODE genomic areas
Neerja Karnani1,
Christopher Taylor1,2,
Ankit Malhotra1,2, and
Anindya Dutta1,3
1 Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, Virginia 22908, USA;
2 Department of Computer Science, University of Virginia, Charlottesville, Virginia 22908, USA
In eukaryotes, accurate control of replication time is required for the efficient completion of S phase and maintenance of genome stability. We present a high-resolution genome-tiling array-based profile of replication timing for 1% of the human genome studied by The ENCODE Project Consortium. Twenty percent of the investigated segments replicate asynchronously (pan-S). These areas are rich in genes and CpG islands, features they share with early-replicating loci. Interphase FISH showed that pan-S replication is a consequence of interallelic variation in replication time and is not an artifact derived from a specific cell cycle synchronization method or from aneuploidy. The interallelic variation in replication time is likely due to interallelic variation in chromatin environment, because while the early- or late-replicating areas were exclusively enriched in activating or repressing histone modifications, respectively, the pan-S areas had both types of histone modification. The replication profile of the chromosomes identified contiguous chromosomal segments of hundreds of kilobases separated by smaller segments where the replication time underwent an acute transition. Close examination of one such segment demonstrated that the delay of replication time was accompanied by a decrease in level of gene expression and appearance of repressive chromatin marks, suggesting that the transition segments are boundary elements separating chromosomal domains with different chromatin environments.
3 Corresponding author.
E-mail ad8q{at}virginia.edu; fax (434) 924-5069.
[Supplemental material is available online at www.genome.org.]
Article is online at http://www.genome.org/cgi/doi/10.1101/gr.5427007

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