The Arabidopsis Histone Chaperone FACT: Role of the HMG-Box Domain of SSRP1.

Autor: Pfab A; Department of Cell Biology & Plant Biochemistry, Biochemistry Centre, University of Regensburg, Universitätsstr. 31, D-93053 Regensburg, Germany., Grønlund JT; Department of Life Sciences, Aalborg University, Sohngaardsholmsvej 49, DK-9000 Aalborg, Denmark., Holzinger P; Department of Cell Biology & Plant Biochemistry, Biochemistry Centre, University of Regensburg, Universitätsstr. 31, D-93053 Regensburg, Germany., Längst G; Department of Biochemistry III, Biochemistry Centre, University of Regensburg, Universitätsstr. 31, D-93053 Regensburg, Germany., Grasser KD; Department of Cell Biology & Plant Biochemistry, Biochemistry Centre, University of Regensburg, Universitätsstr. 31, D-93053 Regensburg, Germany. Electronic address: Klaus.Grasser@ur.de.
Jazyk: angličtina
Zdroj: Journal of molecular biology [J Mol Biol] 2018 Aug 17; Vol. 430 (17), pp. 2747-2759. Date of Electronic Publication: 2018 Jun 30.
DOI: 10.1016/j.jmb.2018.06.046
Abstrakt: Histone chaperones play critical roles in regulated structural transitions of chromatin in eukaryotic cells that involve nucleosome disassembly and reassembly. The histone chaperone FACT is a heterodimeric complex consisting in plants and metazoa of SSRP1/SPT16 and is involved in dynamic nucleosome reorganization during various DNA-dependent processes including transcription, replication and repair. The C-terminal HMG-box domain of the SSRP1 subunit mediates interactions with DNA and nucleosomes in vitro, but its relevance in vivo is unclear. Here, we demonstrate that Arabidopsis ssrp1-2 mutant plants express a C-terminally truncated SSRP1 protein. Although the structure of the truncated HMG-box domain is distinctly disturbed, it still exhibits residual DNA-binding activity, but has lost DNA-bending activity. Since ssrp1-2 plants are phenotypically affected but viable, the HMG-box domain may be functionally non-essential. To examine this possibility, SSRP1∆HMG completely lacking the HMG-box domain was studied. SSRP1∆HMG in vitro did not bind to DNA and its interactions with nucleosomes were severely reduced. Nevertheless, the protein showed a nuclear mobility and protein interactions similar to SSRP1. Interestingly, expression of SSRP1∆HMG is almost as efficient as that of full-length SSRP1 in supporting normal growth and development of the otherwise non-viable Arabidopsis ssrp1-1 mutant. SSRP1∆HMG is structurally similar to the fungal ortholog termed Pob3 that shares clear similarity with SSRP1, but it lacks the C-terminal HMG-box. Therefore, our findings indicate that the HMG-box domain conserved among SSRP1 proteins is not critical in Arabidopsis, and thus, the functionality of SSRP1/SPT16 in plants/metazoa and Pob3/Spt16 in fungi is perhaps more similar than anticipated.
(Copyright © 2018 Elsevier Ltd. All rights reserved.)
Databáze: MEDLINE
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