α-Synuclein misfolding and aggregation is a hallmark in Parkinson's disease and in several other neurodegenerative diseases known as synucleinopathies. The toxic properties of α-synuclein are conserved from yeast to man, but the precise underpinnings of the cellular pathologies associated are still elusive, complicating the development of effective therapeutic strategies. Combining molecular genetics with target-based approaches, we established that glycation, an unavoidable age-associated post-translational modification, enhanced α-synuclein toxicity in vitro and in vivo, in Drosophila and in mice. Glycation affected primarily the N-terminal region of α-synuclein, reducing membrane binding, impaired the clearance of α-synuclein, and promoted the accumulation of toxic oligomers that impaired neuronal synaptic transmission. Strikingly, using glycation inhibitors, we demonstrated that normal clearance of α-synuclein was re-established, aggregation was reduced, and motor phenotypes in Drosophila were alleviated. Altogether, our study demonstrates glycation constitutes a novel drug target that can be explored in synucleinopathies as well as in other neurodegenerative conditions.

Sirtuin genes have been associated with aging and are known to affect multiple cellular pathways. Sirtuin 2 was previously shown to modulate proteotoxicity associated with age-associated neurodegenerative disorders such as Alzheimer and Parkinson disease (PD). However, the precise molecular mechanisms involved remain unclear. Here, we provide mechanistic insight into the interplay between sirtuin 2 and α-synuclein, the major component of the pathognomonic protein inclusions in PD and other synucleinopathies. We found that α-synuclein is acetylated on lysines 6 and 10 and that these residues are deacetylated by sirtuin 2. Genetic manipulation of sirtuin 2 levels in vitro and in vivo modulates the levels of α-synuclein acetylation, its aggregation, and autophagy. Strikingly, mutants blocking acetylation exacerbate α-synuclein toxicity in vivo, in the substantia nigra of rats. Our study identifies α-synuclein acetylation as a key regulatory mechanism governing α-synuclein aggregation and toxicity, demonstrating the potential therapeutic value of sirtuin 2 inhibition in synucleinopathies.

Background: Chromatin-HP1 (heterochromatin protein 1) interaction is crucial for heterochromatin assembly. Results: hHP1␤ uses alternative interfaces to bind nucleosomes depending on histone 3 methylation within a highly dynamic complex. Conclusion: hHP1␤ explores chromatin for sites of methyl-mark enrichment where it can bind histone 3 tails from adjacent nucleosomes. Significance: We provide a conceptual framework to understand the molecular basis of dynamic interactions regulated by histone modification.

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1 1 a r t i c l e sSplicing entails the removal of introns from pre-mRNAs to generate exon-only mRNA, which is exported out of the nucleus for translation 1 . The splicing process is driven and controlled by a large and dynamic RNA-protein complex, the spliceosome 1,2 . The composition and structure of the spliceosome undergoes multiple rearrangements during a splicing reaction, in which a set of distinct structural and compositional states, designated as E, A, B act , B* and C complexes, can be defined 1 . As part of this process, small nuclear ribonucleoprotein (snRNP) particles and non-snRNP splice factors are recruited and released 1,2 . Although the organization of snRNP components of the spliceosome has received considerable attention in recent years, very little is known about the assembly, structure and dynamics of non-snRNP multimeric complexes.The non-snRNP RES complex is present in humans and yeast 3,4 . Deletion of RES genes slows splicing and leads to pre-mRNA leakage into the cytoplasm 3-5 . Distinct introns exhibit RES-dependent splicing 5-9 , as do pre-mRNAs encoding proteins functioning in RNA-nucleotide metabolism 8,10 . Components of the RES complex are found in B and C complexes of the spliceosome, in which RES can interact with U2 snRNP 4,11,12 . In yeast, the RES complex is composed of three proteins, snRNP-associated protein 17 (Snu17p, also known as Ist3p), pre-mRNA-leakage protein 1 (Pml1p) and bud siteselection protein 13 (Bud13p) 3,4 . Snu17p and Bud13p have been implicated directly in splicing 3,5,13 , whereas Pml1p has been linked to the retention of unspliced pre-mRNA in the nucleus 3,5 . Caenorhabditis elegans Bud13p is involved in embryogenesis 14 .Sequence analysis has indicated that Snu17p is a 148-residue (17.1-kDa) noncanonical member of the RRM family of proteins with a long C-terminal part, which exhibits low sequence similarity to published RRM structures 4 . Snu17p binds with nanomolar affinity to the 266-residue (30.5-kDa), natively disordered protein Bud13p 15 . The interaction has been postulated to involve a C-terminal UHM-ligand motif (ULM) in Bud13p that interacts with a U2AF-homology motif (UHM) in the RRM domain of Snu17p 13,15,16 . The only other identified domain encompasses a stretch of lysine residues at the N terminus of Bud13p. Binding of the third component, the 204-residue (23.4-kDa) Pml1p, occurs through its 50 N-terminal disordered residues. The remainder of Pml1p folds as a forkhead-associated domain 13,15,17 , which could potentially bind phosphopeptides 17 . Biochemical evidence has suggested that Snu17p acts as the central binding platform, which interacts with disordered parts of Bud13p and Pml1p 13,15,16 . The precise molecular architecture of the RES complex, however, has been elusive, and its RNA binding capabilities have remained unexplored.Here we solved the three-dimensional structure of the core of the RES complex and demonstrated that its assembly is driven by cooperativity that increases the binding affinity of the components of the complex ...

Familial and idiopathic Parkinson's disease (PD) is associated with the abnormal neuronal accumulation of α-synuclein (aS) leading to β-sheet-rich aggregates called Lewy Bodies (LBs). Moreover, single point mutation in aS gene and gene multiplication lead to autosomal dominant forms of PD. A connection between PD and the 14-3-3 chaperone-like proteins was recently proposed, based on the fact that some of the 14-3-3 isoforms can interact with genetic PD-associated proteins such as parkin, LRRK2 and aS and were found as components of LBs in human PD. In particular, a direct interaction between 14-3-3η and aS was reported when probed by co-immunoprecipitation from cell models, from parkinsonian brains and by surface plasmon resonance in vitro. However, the mechanisms through which 14-3-3η and aS interact in PD brains remain unclear. Herein, we show that while 14-3-3η is unable to bind monomeric aS, it interacts with aS oligomers which occur during the early stages of aS aggregation. This interaction diverts the aggregation process even when 14-3-3η is present in sub-stoichiometric amounts relative to aS. When aS level is overwhelmingly higher than that of 14-3-3η, the fibrillation process becomes a sequestration mechanism for 14-3-3η, undermining all processes governed by this protein. Using a panel of complementary techniques, we single out the stage of aggregation at which the aS/14-3-3η interaction occurs, characterize the products of the resulting processes, and show how the processes elucidated in vitro are relevant in cell models. Our findings constitute a first step in elucidating the molecular mechanism of aS/14-3-3η interaction and in understanding the critical aggregation step at which 14-3-3η has the potential to rescue aS-induced cellular toxicity.

Background: α-Synuclein aggregation is associated with Parkinson disease.Results: Small molecules were identified by second-harmonic generation (SHG) that change α-synuclein conformation in vitro and reduce the aggregation of protein in cells.Conclusion: Conformation plays a role in α-synuclein aggregation in cells.Significance: Small molecules that modulate the conformation of α-synuclein and reduce its aggregation could be developed into therapeutics for Parkinson disease.

In the brain of individuals with Alzheimer's disease, the regulatory protein ubiquitin is found conjugated to different lysine residues of tau protein assembled into pathological paired helical filaments. To shed light on the hitherto unexplored ubiquitination‐linked conformational transitions of tau, the availability of in vitro ubiquitin conjugation methods is of primary importance. In our work, we focused on the four‐repeat domain of tau and assembled an enzymatic machinery formed by UBE1, Ubc13, and CHIP enzymes. The enzymatic reaction resulted in monoubiquitination at multiple sites, reminiscent of the ubiquitination pattern observed in vivo. We further exploited chemoselective disulfide coupling reactions to construct three tau regioisomers with site‐specific monoubiquitination. Protein aggregation experiments revealed that the multiple enzyme‐derived products were unable to convert into amyloid fibrils, while the semisynthetic conjugates exhibited diverse capability to form filaments. This study contributes novel insight into the effects of a key post‐translational modification on aberrant protein self‐assembly.