Overall changes in chromatin sensitivity to DNase I during differentiation

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• Chromatin structure plays a crucial role in regulating gene expression.
• DNase I sensitivity is a common method to assess chromatin accessibility.
• Cell differentiation involves significant changes in chromatin organization.

Purpose of the Study:

• To investigate the changes in DNase I sensitivity of total chromatin during cellular differentiation.
• To compare DNase I sensitivity between proliferating and terminally differentiated cells.
• To examine the impact of differentiation on the accessibility of specific genes, such as c-myc.

Main Methods:

• Measuring labeled nucleotide incorporation into DNase-sensitive sites.
• Electrophoresis of DNA from DNase-treated nuclei.
• Development of a novel flow-cytometric technique for cell-level DNase sensitivity analysis.

Main Results:

• Terminally differentiated cells exhibited reduced DNase I sensitivity compared to proliferating cells.
• DMSO-induced differentiation of HL60 leukemia cells decreased chromatin digestibility.
• A novel flow-cytometric method confirmed reduced DNase I sensitivity in differentiated cells, independent of cell cycle phase.
• Specific hypersensitive sites near the c-myc gene were partially lost upon differentiation.

Conclusions:

• Terminal differentiation is associated with progressive chromatin condensation.
• This condensation leads to gradual inactivation of specific genes.
• DNase I sensitivity serves as a valuable indicator of chromatin changes during differentiation.