Fine tuning gene expression through short DNA-protein binding cycles

Area of Science:

• Molecular Biology
• Genetics
• Biophysics

Background:

• Transcription factors (TFs) were previously thought to bind DNA in a stepwise manner for transcription initiation.
• Recent studies reveal TFs interact with DNA in living cells via very short binding cycles.
• These rapid cycles are driven by active dissociation mechanisms, suggesting crucial biological roles.

Purpose of the Study:

• To explore the interpretation that short TF binding cycles favor gene expression determinism.
• To investigate how TF dynamics influence gene expression dosage.
• To propose conditions that increase the frequency of DNA-protein binding cycles.

Main Methods:

• Analysis of TF-DNA interactions in living cells.
• Comparison of in vivo binding dynamics with in vitro data.
• Modeling of TF turnover and its effect on gene expression.

Main Results:

• Short TF binding cycles, triggered by active dissociation, contrast with previous in vitro models.
• The dynamics of promoter occupancy versus protein accumulation are critical for gene expression dosage in open chromatin.
• Proposed biological activities and quantitative conditions can increase DNA-protein binding cycle frequency.

Conclusions:

• The brevity of TF turnover favors gene expression determinism.
• Differential dynamics between promoter occupancy and protein accumulation are key for gene expression dosage.
• These TF dynamics offer a model for apparent gradation of single-site occupancy, extending mass action principles to low molecule numbers.