Nucleosomal arrangement affects single-molecule transcription dynamics

Transcription is the first step toward protein production. During transcription, a polymerase enzyme moves along DNA and copies it to RNA. In the cell, DNA is highly compacted: roughly 150 bp of DNA is wrapped around histone proteins to form a nucleosome. However, little is known about how closely spaced nucleosomes impact polymerase transcription. We performed single-molecule optical tweezers transcription experiments on dinucleosomal DNA templates. We show that the effect of the second nucleosome on polymerase transcription efficiency through the first one depends on the internucleosomal spacing and the rotational arrangement of the nucleosomes on the helical DNA template. Our findings provide insights into how DNA compaction affects transcription in vitro.