S-phase transcriptional buffering quantified on two different promoters

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• Quantitative fluorescence imaging enables study of gene expression kinetics in single cells.
• Previous work showed reduced mRNA transcription post-replication, a homeostasis mechanism.
• This buffering relates transcription levels to cell cycle stage and allele number.

Purpose of the Study:

• To investigate how S phase transcriptional buffering affects different promoters (cytomegalovirus vs. cyclin D1).
• To determine if histone modifications can alter replication-induced transcription down-regulation.
• To compare transcriptional potential versus actual activity in fixed and living cells.

Main Methods:

• In vivo visualization of mammalian mRNA transcriptional kinetics at single-gene resolution.
• Utilizing a cell system to track transcription during the cell cycle.
• Employing quantitative fluorescence-based techniques for measuring transcription levels.

Main Results:

• Global histone modification modulation reversed transcription down-regulation during replication.
• Transcriptional potential in both fixed and living cells was higher than observed transcription.
• Promoters may be intrinsically limited from achieving maximal transcriptional output.

Conclusions:

• Transcriptional buffering during S phase is promoter-dependent and can be overcome by histone modification.
• Gene promoters may operate below their maximal capacity under normal cellular conditions.
• Understanding these regulatory mechanisms is key to gene expression control.