New insights into replication origin characteristics in metazoans.

Area of Science:

• Genetics
• Molecular Biology
• Bioinformatics

Background:

• DNA replication origins (Oris) are essential for cell division.
• Previous work identified GC-rich elements in metazoan Oris.

Purpose of the Study:

• To characterize GC-rich elements as origin G-rich repeated elements (OGREs).
• To investigate the precise location of DNA synthesis initiation relative to OGREs.
• To explore the association of OGREs with CpG islands and replication timing.

Main Methods:

• Bioinformatic analysis of DNA replication origins.
• Sequence element identification and characterization.
• Correlation analysis with replication timing data.

Main Results:

• GC-rich elements identified as OGREs, present in 67-90% of Oris from Drosophila to humans.
• DNA synthesis initiation occurs precisely 160 bp (Drosophila) and 280 bp (mouse) from OGREs.
• OGREs in CpG islands have opposite orientations, with two initiation sites; Oris without CpG islands have one initiation site.
• OGRE density correlates with replication timing; OGREs predict high nucleosome occupancy and G-quadruplex structures.

Conclusions:

• OGREs are conserved sequence elements critical for DNA replication origin function across metazoans.
• OGREs' position and orientation influence initiation site selection, especially in CpG islands.
• OGREs may act as structural elements controlling replication origin choice and activation through G-quadruplex formation.