Abundance and distribution of RNA polymerase II in Arabidopsis interphase nuclei

J Exp Bot. 2015 Mar;66(6):1687-98. doi: 10.1093/jxb/erv091. Epub 2015 Mar 4.

Abstract

RNA polymerase II (RNAPII) is responsible for the transcription of most eukaryotic protein-coding genes. Analysing the topological distribution and quantification of RNAPII can contribute to understanding its function in interphase nuclei. Previously it was shown that RNAPII molecules in plant nuclei form reticulate structures within euchromatin of differentiated Arabidopsis thaliana nuclei rather than being organized in distinct 'transcription factories' as observed in mammalian nuclei. Immunosignal intensity measurements based on specific antibody labelling in maximum intensity projections of image stacks acquired by structured illumination microscopy (SIM) suggested a relative proportional increase of RNAPII in endopolyploid plant nuclei. Here, photoactivated localization microscopy (PALM) was applied to determine the absolute number and distribution of active and inactive RNAPII molecules in differentiated A. thaliana nuclei. The proportional increase of RNAPII during endopolyploidization is confirmed, but it is also shown that PALM measurements are more reliable than those based on SIM in terms of quantification. The single molecule localization results show that, although RNAPII molecules are globally dispersed within plant euchromatin, they also aggregate within smaller distances as described for mammalian transcription factories.

Keywords: Arabidopsis thaliana; RNA polymerase II; endopolyploidy; photoactivated localization microscopy; structured illumination microscopy; transcription factory..

MeSH terms

  • Arabidopsis / genetics*
  • Arabidopsis / metabolism
  • Arabidopsis Proteins / genetics*
  • Arabidopsis Proteins / metabolism
  • Cell Nucleus / metabolism
  • Interphase
  • Polyploidy*
  • RNA Polymerase II / genetics*
  • RNA Polymerase II / metabolism

Substances

  • Arabidopsis Proteins
  • RNA Polymerase II