Dynamic architecture of the yeast cell cycle uncovered by wavelet decomposition of expression microarray data

Area of Science:

• Systems Biology
• Molecular Biology
• Genomics

Background:

• Understanding the temporal dynamics of gene expression is crucial for deciphering cellular processes.
• Previous studies on the yeast cell cycle have focused on its overall periodicity, but sub-cycle oscillations remain less understood.

Purpose of the Study:

• To investigate large-scale temporal structures and oscillations in yeast mRNA levels during the cell cycle.
• To identify the predominant periodicities governing gene expression within the yeast cell cycle.

Main Methods:

• Application of wavelet analysis to yeast cell cycle expression microarray data from 6178 genes.
• Visualization of gene expression transitions using contour maps plotted against cell cycle time.
• Time-frequency analysis using wavelet transforms for detailed dissection of gene expression profiles.

Main Results:

• Ubiquitous oscillations in mRNA levels were detected, with a predominant period of approximately 40 minutes, a sub-multiple of the cell cycle.
• Transitions in gene expression occurred at approximately 40-minute intervals, appearing as bands across two cell cycles.
• Over two-thirds of genes, including cyclins, exhibited this half-cell cycle periodicity.

Conclusions:

• The yeast cell cycle's gene expression is primarily regulated by a higher-frequency 40-minute oscillation, not the overall cell cycle length.
• This fundamental period appears to be an emergent property of dynamic interactions within the yeast transcriptome.
• Gene expression and cell cycle events may be governed by an underlying attractor with this emergent periodicity.