Hho1p, the linker histone of Saccharomyces cerevisiae, is important for the proper chromatin organization in vivo

Despite the existence of certain differences between yeast and higher eukaryotic cells a considerable part of our knowledge on chromatin structure and function has been obtained by experimenting on Saccharomyces cerevisiae. One of the peculiarities of S. cerevisiae cells is the unusual and less abundant linker histone, Hho1p. Sparse is the information about Hho1p involvement in yeast higher-order chromatin organization. In an attempt to search for possible effects of Hho1p on the global organization of chromatin, we have applied Chromatin Comet Assay (ChCA) on HHO1 knock-out yeast cells. The results showed that the mutant cells exhibited highly distorted higher-order chromatin organization. Characteristically, linker histone depleted chromatin generally exhibited longer chromatin loops than the wild-type. According to the Atomic force microscopy data the wild-type chromatin appeared well organized in structures resembling quite a lot the “30-nm” fiber in contrast to HHO1 knock-out yeast.

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► We trace the role of Saccharomyces cerevisiae linker histone, Hho1p.
► We study the global chromatin organization at the higher-levels of its compaction.
► The lack of Hho1p leads to longer chromatin loops.
► Hho1p is essential for the maintenance of the “30 nm” fiber.