Comprehensive Analysis of Stability and Variability of DNA Minimal I-Motif Structures.

Area of Science:

• Biochemistry
• Molecular Biology
• Genomics

Background:

• Cytosine-rich DNA sequences are known to form i-motif structures, crucial for gene regulation.
• While consecutive C residues are considered essential, some sequences lacking C-tracts can form minimal i-motif structures.

Purpose of the Study:

• To systematically investigate the sequence variability and stability of minimal i-motif-forming DNA.
• To understand the role of polyamines, like spermine, in stabilizing these structures.

Main Methods:

• DNA thermal melting temperature measurements to assess structural stability.
• Analysis of sequence modifications, including bulges, loops, and dangling ends.

Main Results:

• Disrupting base tetrads or their stacking interactions prevents stable i-motif formation.
• Spermine effectively restores stability in minimal i-motif structures with sequence variations.
• Modifications to sequence context and loop length are challenging for stability.

Conclusions:

• Minimal i-motif formation is sequence-variable and facilitated by polyamine-rich environments, such as the mammalian cell nucleus.
• Findings aid in identifying non-canonical i-motif forming sites in genomes.
• Provides insights into i-motif interactions with biological polyamines.