Analysis of the penetrable space within the nucleus

Area of Science:

• Cell Biology
• Molecular Biology
• Biophysics

Background:

• Understanding nuclear and chromatin structure is crucial for gene regulation.
• Previous methods lacked resolution to precisely define internal nuclear spaces.

Purpose of the Study:

• To compare the cavity systems within intact nuclei and isolated chromatin.
• To investigate the penetrability of enzymes like DNase-I into nuclear structures.

Main Methods:

• Utilized radioactive glycogen molecules as passive probes.
• Measured microspace effective diameters in isolated chromatin and intact nuclei.
• Simulated nuclear structure to explain enzyme resistance patterns.

Main Results:

• Isolated chromatin exhibits microspaces with mean diameters of 4.0-4.5 nm.
• Intact nuclei possess larger free spaces, averaging 11.0-15.0 nm in diameter.
• DNase-I (4.1 nm diameter) penetrates intact nuclei despite limited attack on undisturbed structure.

Conclusions:

• Intact nuclei contain significantly larger spaces than isolated chromatin.
• DNase-I resistance in nuclei is attributed to an ordered, compact local chromatin structure with interspersed larger spaces.
• This organization suggests functional implications for nuclear structure and accessibility.