Structural and functional insights into nuclear role of Parkinson’s Disease-associated α-Synuclein

α-Synuclein (αSyn) plays a critical role in the pathogenesis of ‘Synucleinopathies’. Although increased nuclear αSyn localization induces neurotoxicity, its definitive physiological role remains elusive. Previous studies on nuclear αSyn are limited to its interactions with individual histones and dsDNA, leaving a significant gap in understanding its interactions with assembled histone H2a-H2b dimer and (H3-H4) ₂ tetramer, as well as its role in chromatin regulation. Here, we demonstrated that αSyn binds specifically to both H2a-H2b and (H3-H4) ₂ with high affinity. Truncation studies revealed that αSyn(1-103) region interacts with (H3-H4) ₂ , while the acidic (121-140) C-terminal end is crucial for H2a-H2b binding. Sequence analysis suggests αSyn-dimer binding region contains a conserved DEF/YxP motif present in other dimer-binding histone chaperones. High-resolution structure of αSyn- dimer binding region with H2a-H2b complex reveals that αSyn adopts two binding modes (BM1 and BM2). In BM-1, αSyn utilizes nucleosomal DNA-binding surface, while in BM-2, it engages with both DNA- and the H3-interaction interface. Additionally, dimer recognition by αSyn overlaps with other dimer-binding histone chaperones, suggesting αSyn’s potential role in the nucleosome assembly/disassembly process.