How does Pol II overcome the nucleosome barrier?

Abstract

DNA packaging into chromatin presents a strong barrier to RNA polymerase II transcription. In this issue of Molecular Cell, Kireeva et al. describe a minimal system to examine polymerase II transcription through a positioned nucleosome and show, surprisingly, that transcription leads to the displacement of an H2A.H2B dimer from the nucleosome without altering nucleosome position.