Genes pulse with activity

Jonathan Chubb, Robert Singer, and colleagues (Albert Einstein College of Medicine, Bronx, NY) have devised a method to view transcription inside individual cells. By removing the effects of population averaging, the method reveals transcriptional pulses of a eukaryotic developmental gene.

Transcription was visualized by inserting upstream stem loops into an endogenous developmentally regulated Dictyostelium gene called dscA. The nascent transcripts were then detected by a GFP fusion protein that binds to the RNA stem loops.

Single-cell analyses revealed discontinuous transcription, or pulses, rather than smooth, uniform expression. Determining the pulse mechanism will require more investigation, but possibilities include reversible chromatin modifications or variations in transcription factor binding.

Pulsing would provide exquisite regulatory control, suggests Singer. “A burst that makes a lot of message might overshoot the amount of protein needed. That can have deleterious...