A DNA unwinding element and an ARS consensus comprise a replication origin within a yeast chromosome

Area of Science:

• Molecular Biology
• Genetics
• Yeast Biology

Background:

• DNA replication is a fundamental biological process.
• Replication origins are crucial initiation sites for DNA replication.
• Understanding replication origin function in chromosomes is essential for comprehending genome stability.

Purpose of the Study:

• To define and characterize a specific replication origin, ORI305, within chromosome III of Saccharomyces cerevisiae.
• To identify the cis-acting DNA elements essential for ORI305 activity in its chromosomal context.
• To elucidate the role of DNA helical instability in replication origin function.

Main Methods:

• Mutational analysis of Saccharomyces cerevisiae chromosome III.
• Assay of replication origin activity using two-dimensional gel electrophoresis of replication intermediates.
• Plasmid-based functional assay of autonomously replicating sequences (ARS).

Main Results:

• ORI305 was defined within chromosome III of Saccharomyces cerevisiae.
• Essential cis-acting elements for ORI305 activity in the chromosome mirror those of ARS305 in plasmids.
• Key elements include an 11 bp ARS consensus match and an adjacent 3' sequence.
• Point mutations in the consensus match inactivate origin function.
• The 3' flanking sequence, crucial for function, exhibits DNA helical instability and acts as a DNA unwinding element.

Conclusions:

• The identified cis-acting elements are critical for specifying replication origin function in the chromosome.
• DNA helical instability within the 3' flanking region is essential for replication origin activity.
• This study provides insights into the mechanism of replication origin initiation in eukaryotic chromosomes.