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bioRxiv · 10.1101/2025.05.13.653634

Structural basis of RNA polymerase II transcription on the H3-H4 octasome

Ho, C.-H.·Nozawa, K.·Nishimura, M.·Oi, M.·Kujirai, T.·Ogasawara, M.·Ehara, H.·Sekine, S.-i.·Takizawa, Y.·Kurumizaka, H.
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Abstract

The H3-H4 octasome is a nucleosome-like particle in which two DNA gyres are wrapped around each H3-H4 tetramer disk, forming a clamshell-like configuration. In the present study, we performed in vitro RNAPII transcription assays with the H3-H4 octasome and found that RNAPII transcribed the H3-H4 octasome more efficiently than the nucleosome. RNAPII paused at only one position, superhelical location (SHL) -4 in the H3-H4 octasome, in contrast to pausing at the SHL(-5), SHL(-2), and SHL(-1) positions in the nucleosome. Cryo-electron microscopy analysis revealed that two H3-H4 tetramer disks are retained when the RNAPII paused at the SHL(-4) position of the H3-H4 octasome. However, when RNAPII reached the SHL(-0.5) position, five base pairs before the dyad position of the H3-H4 octasome, the proximal H3-H4 tetramer was disassembled but the distal H3-H4 tetramer still remained on the DNA. Therefore, RNAPII efficiently transcribes the H3-H4 octasome by stepwise H3-H4 tetramer disassembly.

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Ho, C.-H., Nozawa, K., Nishimura, M., Oi, M., Kujirai, T., Ogasawara, M., Ehara, H., Sekine, S.-i., Takizawa, Y., Kurumizaka, H.. 2025-05-13. Structural basis of RNA polymerase II transcription on the H3-H4 octasome. https://doi.org/10.1101/2025.05.13.653634

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