Oscillatory expression of Hes1, p53, and NF-kappaB driven by transcriptional time delays

Area of Science:

• Molecular Biology
• Systems Biology
• Biophysics

Background:

• Gene expression is often regulated by feedback inhibition, where a gene's product downregulates its own expression.
• Eukaryotic gene regulation involves time delays (transcription, splicing, translation), which can theoretically cause expression oscillations.
• Experimental evidence for delay-driven oscillations in gene expression has been scarce.

Purpose of the Study:

• To investigate the role of time delays in driving oscillatory gene expression in eukaryotic cells.
• To provide experimental evidence supporting the hypothesis that delays, not additional regulatory components, cause observed oscillations.
• To analyze the impact of delays on the characteristics of gene expression oscillations.

Main Methods:

• Utilized mathematical modeling informed by recent experimental data.
• Focused on short feedback inhibition loops involving specific proteins (Hes1, p53, NF-kappaB).
• Analyzed the relationship between delays, half-lives, and oscillation periods.

Main Results:

• Mathematical modeling strongly suggests transcriptional delays are the primary drivers of observed oscillatory expression and activity for Hes1, p53, and NF-kappaB.
• The oscillatory period is primarily determined by the delay and mRNA/protein half-lives.
• Delayed models explain oscillations without needing extra feedback loop components, unlike non-delayed models.

Conclusions:

• Provides direct evidence that transcriptional delays can drive oscillatory gene activity in eukaryotic cells.
• Highlights the critical importance of incorporating time delays when analyzing genetic regulatory networks.
• Suggests delays are key factors in processes like developmental pattern formation involving feedback inhibition.