Real-Time Dynamics of RNA Polymerase II Clustering in Live Human Cells

Abstract

Pol II Micro Clusters In higher eukaryotes, messenger RNA (mRNA) synthesis is thought to involve foci of clustered RNA polymerase II (Pol II) called transcription factories. However, clustered Pol II have not been resolved in living cells, raising the debate about their existence in vivo and what role, if any, they play in nuclear organization and regulation of gene expression. Cisse et al. (p. 664 , published online 4 July; see the Perspective by Rickman and Bickmore ) developed single-molecule in vivo analyses revealing the distribution and dynamics of Pol II clustering in living cells. Pol II clusters were smaller than the diffraction limit (<250 nm). Transient dynamics of the Pol II clusters, and correlation with changes in transcription, pointed to a role in transcription initiation rather than in elongation.