Deoxyribonuclease I generates single-stranded gaps in chromatin deoxyribonucleic acid

Area of Science:

• Molecular Biology
• Chromatin Structure and Dynamics

Background:

• DNase I digestion of chromatin paradoxically generates 10-base multiple DNA ladder fragments.
• Previous models fail to explain this phenomenon or the substantial production of single-stranded DNA during DNase I digestion.

Purpose of the Study:

• To present and validate a novel single-stranded gap model for DNase I digestion of chromatin.
• To explain the generation of DNA ladder fragments and single-stranded DNA production.

Main Methods:

• Utilized S1 nuclease sensitivity assays to assess ladder fragment composition.
• Employed NAD+-dependent ligase and T4 ligase to verify gap separation at fragment termini.
• Performed electron microscopy with cytochrome c and gene 32 protein labeling to visualize and characterize single-stranded gaps.

Main Results:

• Confirmed DNase I produces single-stranded gaps in chromatin DNA.
• Demonstrated that termini of 10-base ladder fragments are separated by single-stranded gaps.
• Electron microscopy revealed single-stranded gaps ranging from 10 to 120 bases, forming a ladder distribution.

Conclusions:

• The single-stranded gap model accurately explains DNA ladder fragment generation and single-stranded DNA production during DNase I digestion.
• DNase I introduces single-stranded gaps into chromatin, influencing DNA fragment characteristics.