Super-resolution imaging of fluorescently labeled, endogenous RNA Polymerase II in living cells with CRISPR/Cas9-mediated gene editing

Sci Rep. 2016 Oct 26:6:35949. doi: 10.1038/srep35949.


Live cell imaging of mammalian RNA polymerase II (Pol II) has previously relied on random insertions of exogenous, mutant Pol II coupled with the degradation of endogenous Pol II using a toxin, α-amanitin. Therefore, it has been unclear whether over-expression of labeled Pol II under an exogenous promoter may have played a role in reported Pol II dynamics in vivo. Here we label the endogenous Pol II in mouse embryonic fibroblast (MEF) cells using the CRISPR/Cas9 gene editing system. Using single-molecule based super-resolution imaging in the living cells, we captured endogenous Pol II clusters. Consistent with previous studies, we observed that Pol II clusters were short-lived (cluster lifetime ~8 s) in living cells. Moreover, dynamic responses to serum-stimulation, and drug-mediated transcription inhibition were all in agreement with previous observations in the exogenous Pol II MEF cell line. Our findings suggest that previous exogenously tagged Pol II faithfully recapitulated the endogenous polymerase clustering dynamics in living cells, and our approach may in principle be used to directly label transcription factors for live cell imaging.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CRISPR-Cas Systems
  • Cells, Cultured
  • Gene Editing / methods
  • Gene Knock-In Techniques
  • Luminescent Proteins / chemistry
  • Luminescent Proteins / genetics
  • Luminescent Proteins / metabolism
  • Mice
  • Microscopy, Fluorescence
  • Protein Aggregates
  • RNA Polymerase II / chemistry
  • RNA Polymerase II / genetics*
  • RNA Polymerase II / metabolism*
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism


  • Dendra2 protein, Dendronephthya
  • Luminescent Proteins
  • Protein Aggregates
  • Recombinant Fusion Proteins
  • RNA Polymerase II