Histone N-terminal tails interfere with nucleosome traversal by RNA polymerase II.

We determined the effect of the N-terminal histone tails on nucleosome traversal by yeast and human RNA polymerase II (pol II). Removal of H2A/H2B tails, H3/H4 tails, or all tails increased complete traversal of the nucleosome by human pol II, although the increase varied considerably depending on the template and on which tails were removed. Human pol II achieved >80% traversal of one nucleosomal template lacking the H2A/H2B tails, but even in those reactions, the transcript elongation rate was lower than the rate on pure DNA templates.