Mammalian DNA enriched for replication origins is enriched for snap-back sequences.

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Understanding DNA replication origins is crucial for cell division and genome stability.
• Nascent DNA isolation techniques are key to studying replication initiation.
• Palindromic sequences, capable of forming snap-back structures, are implicated in various DNA processes.

Purpose of the Study:

• To investigate the presence of palindromic sequences at mammalian DNA replication origins.
• To determine if nascent DNA enriched for replication origins also contains snap-back DNA.

Main Methods:

• Isolation of double-stranded nascent DNA using replication loop instability.
• Denaturation of isolated DNA to identify snap-back sequences (single-stranded DNA with inverted repeats).
• Assay of snap-back sequences using hydroxyapatite chromatography in mouse, rat, and monkey cells.

Main Results:

• DNA enriched for replication origins demonstrated enrichment for snap-back sequences.
• Snap-back DNA reassociates rapidly into stem-loop structures under renaturing conditions.
• The presence of snap-back sequences was confirmed in both synchronously and asynchronously growing cells.

Conclusions:

• Mammalian DNA replication origins are likely associated with palindromic sequences.
• Snap-back DNA enrichment in origin-enriched DNA supports the role of palindromes in replication initiation.
• These findings provide insights into the structural features of DNA replication origins.