Free energy profile for nucleosomal DNA unwrapping

Kono, Hidetoshi; Yonetani, Yoshiteru; Ikebe, Kimiyoshi; Sakuraba, Shun; Ishida, Hisashi

Eukaryotic Genome is stored in a nucleus in the form of chromatin. Along with DNA binding proteins, this chromatin structure plays a key role in gene regulation. The chromatin has the fundamental structural unit called nucleosome which is composed of two copies of histones H2A, H2B, H3 and H4 and DNA wrapped around the histone proteins almost twice. Transcription does not occur until nucleosome is unwrapped to expose DNA, which can then be recognized by regulatory proteins. To understand this unwrapping process, MD simulations were performed on two nucleosomes: the canonical H3 and the H3 variant called CENP-A, essential for the kinetochore assembly. In the talk, how these nucleosomes are different in free energy profiles and what causes the differences are discussed.