Abstract
Chromatin structure is dictated by nucleosome assembly and internucleosomal interactions. The tight wrapping of nucleosomes inhibits gene expression, but modifications to histone tails modulate chromatin structure, allowing for proper genetic function. The histone H4 tail is thought to play a large role in regulating chromatin structure. Here we investigated the structure of nucleosomes assembled with a tail-truncated H4 histone using Atomic Force Microscopy. We assembled tail-truncated H4 nucleosomes on DNA templates allowing for the assembly of mononucleosomes or dinucleosomes. Mononucleosomes assembled on nonspecific DNA led to decreased DNA wrapping efficiency. This effect is less pronounced for nucleosomes assembled on positioning motifs. Dinucleosome studies resulted in the discovery of two effects- truncation of the H4 tail does not diminish the preferential positioning observed in full-length nucleosomes, and internucleosomal interaction eliminates the DNA unwrapping effect. These findings provide insight on the role of histone H4 in chromatin structure and stability.
Highlights
Chromatin structure is dictated by nucleosome assembly and internucleosomal interactions
In this study we revealed the role of the histone H4 tail in nucleosome structure and internucleosomal interaction with the use of Atomic Force Microscopy (AFM)
We found that truncation of the H4 tail changes the wrapping efficiency of nucleosomes
Summary
Chromatin structure is dictated by nucleosome assembly and internucleosomal interactions. Dinucleosome studies resulted in the discovery of two effects- truncation of the H4 tail does not diminish the preferential positioning observed in full-length nucleosomes, and internucleosomal interaction eliminates the DNA unwrapping effect. These findings provide insight on the role of histone H4 in chromatin structure and stability. Despite the role of histone H4 in these interactions, it has been reported that complete truncation of the histone tail does not significantly affect nucleosome structure; these conclusions were reported on mononucleosome results of simulations[22] and assembled on positioning sequences[23]. The implications of these data on nucleosome structure and internucleosomal interaction are discussed
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