Nudging through a nucleosome
Medieval monks feverishly transcribing Latin into Olde English would identify with the struggles that the eukaryotic RNA polymerase II complex must overcome in order to write DNA in the language of RNA. While theirs was a conceptual barrier, that of RNA polymerase II is quite physical and embodied by nucleosomes. Much like string wrapped around a spool, nucleosomes consist of a cylindrical protein core and DNA wrapped tightly around it. On page 626 of this issue, Hodges et al. (1) report single-molecule measurements that help to elucidate how the nucleosomal DNA is transcribed.