CpG Islands: Starting Blocks for Replication and Transcription

Marie-Noëlle Prioleau

doi:10.1371/journal.pgen.1000454

Abstract

ORI sequences. A few months ago, common features shared by large groups of ORIs were extracted from a large-scale mapping of replication origins based on the resistance of short nascent strands (SNS) to l-exonuclease digestion [5]. This study, conducted in HeLa cells and covering approximately 1% of the human genome, showed that origin density is strongly correlated with genomic landscapes, with clusters of closely spaced origins in GC-rich regions and no or only few origins in GC-poor regions. Moreover, half of the origins were mapped within or near CpG islands. In this issue of PLoS Genetics, a study by Sequeira-Mendes et al. extends this obser

Highlights

The ongoing release of numerous genome sequences constitutes a scientific landmark that has transformed our way of thinking about the organization of living matter
What is true for a specific ORI can be misleading for the majority of ORIs because of the flexibility of mechanisms that are involved in origin selection
A few months ago, common features shared by large groups of ORIs were extracted from a large-scale mapping of replication origins based on the resistance of short nascent strands (SNS) to l-exonuclease digestion [5]

Summary

Introduction

The ongoing release of numerous genome sequences constitutes a scientific landmark that has transformed our way of thinking about the organization of living matter. Only a very small number of ORIs had been mapped, hindering the development of an accurate and global view of origin specification. A recent study showed that 20% of the mouse genome displayed important changes in replication timing upon differentiation of embryonic stem (ES) cells, suggesting a highly dynamic regulation [4].

Results

Conclusion