The structural basis of human Spt16 N-terminal domain interaction with histone (H3-H4)2 tetramer

FACT (Facilitates Chromatin Transactions) is a heterodimeric protein complex involved in RNA poly-merase H transcription elongation, playing essential roles in chromatin remodeling during transcription, replication, and DNA damage repair. The FACT subunit hSpt16 is essential for nucleosome reorganization. The N-terminal domain of hSpt16 (hSpt16-NTD) was recently described as a histone (H3-H4)(2)-binding domain; however, its mode of interaction remains unknown. In this study, we solved the structure of hSpt16-NTD437 at 2.19 angstrom and found that a long-disordered region (hSpt16-LDR), after the main body of hSpt16-NTD, is a novel histone-binding motif. Furthermore, hSpt16-LDR interaction with (H3-H4)(2) is H3 N-terminal tail-independent. Therefore, Spt16-NTD is a histone H3-H4-specific binding domain with a distinct mechanism of interaction between histones and histone chaperones. (C) 2018 Elsevier Inc. All rights reserved.