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Understanding the normal function of the Huntingtin (HTT) protein is of significance in the design and implementation of therapeutic strategies for Huntington's disease (HD). Expansion of the CAG repeat in the HTT gene, encoding an expanded polyglutamine (polyQ) repeat within the HTT protein, causes HD and may compromise HTT's normal activity contributing to HD pathology. Here, we investigated the previously defined role of HTT in autophagy specifically through studying HTT's association with ubiquitin. We find that HTT interacts directly with ubiquitin in vitro. Tandem affinity purification was used to identify ubiquitinated and ubiquitin-associated proteins that copurify with a HTT N-terminal fragment under basal conditions. Copurification is enhanced by HTT polyQ expansion and reduced by mimicking HTT serine 421 phosphorylation. The identified HTT-interacting proteins include RNA-binding proteins (RBPs) involved in mRNA translation, proteins enriched in stress granules, the nuclear proteome, the defective ribosomal products (DRiPs) proteome and the brain-derived autophagosomal proteome. To determine whether the proteins interacting with HTT are autophagic targets, HTT knockout (KO) cells and immunoprecipitation of lysosomes were used to investigate autophagy in the absence of HTT. HTT KO was associated with reduced abundance of mitochondrial proteins in the lysosome, indicating a potential compromise in basal mitophagy, and increased lysosomal abundance of RBPs which may result from compensatory up-regulation of starvation-induced macroautophagy. We suggest HTT is critical for appropriate basal clearance of mitochondrial proteins and RBPs, hence reduced HTT proteostatic function with mutation may contribute to the neuropathology of HD.

Huntingtons disease (HD) is an inherited neurodegenerative disorder caused by an expanded CAG repeat in the huntingtin (HTT) gene. The repeat-expanded HTT encodes a mutated HTT (mHTT), which is known to induce DNA double-strand breaks (DSBs), activation of the cGAS-STING pathway, and apoptosis in HD. However, the mechanism by which mHTT triggers these events is unknown. Here, we show that HTT interacts with both exonuclease 1 (Exo1) and MutLα (MLH1-PMS2), a negative regulator of Exo1. While the HTT-Exo1 interaction suppresses the Exo1-catalyzed DNA end resection during DSB repair, the HTT-MutLα interaction functions to stabilize MLH1. However, mHTT displays a significantly reduced interaction with Exo1 or MutLα, thereby losing the ability to regulate Exo1. Thus, cells expressing mHTT exhibit rapid MLH1 degradation and hyperactive DNA excision, which causes severe DNA damage and cytosolic DNA accumulation. This activates the cGAS-STING pathway to mediate apoptosis. Therefore, we have identified unique functions for both HTT and mHTT in modulating DNA repair and the cGAS-STING pathway-mediated apoptosis by interacting with MLH1. Our work elucidates the mechanism by which mHTT causes HD.

The field of Huntingtons disease research covers many different scientific disciplines, from molecular biology all the way through to clinical practice, and as our understanding of the disease has progressed over the decades, a great deal of different terminology has accrued. The field is also renowned for its collaborative spirit and use of standardized reagents, assays, datasets, models, and clinical measures, so the use of standardized terms is especially important. We have set out to determine, through a consensus exercise involving basic and clinical scientists working in the field, the most appropriate language to use across disciplines. Nominally, this article will serve as the style guide for the Journal of Huntingtons Disease (JHD), the only journal devoted exclusively to HD, and we lay out the preferred and standardized terminology and nomenclature for use in JHD publications. However, we hope that this article will also serve as a useful resource to the HD research community at large and that these recommended naming conventions will be adopted widely.

Post-translational modifications (PTMs) of proteins play a significant role in normal protein function but can also be instrumental in disease pathogenesis. One critical yet under-studied PTM in disease is ubiquitination. Ubiquitin chain addition and substrate specificity are determined by a large spectrum of ubiquitin-ligating and -modifying enzymes, E3 ligases, whose expression levels and activities are tightly regulated in a cell-specific manner. While most ubiquitin chains can target proteins for proteasomal degradation, ubiquitination can contribute to other functions within the cell, including protein localization, protein activity, endocytosis, transcription, and autophagy. One E3 ligase, UBE3A, has garnered much attention because of its involvement in learning and memory, as well as its association with neurodevelopmental autism spectrum disorders (ASDs). However, more recent findings have suggested a potential involvement of UBE3A in neurodegenerative proteinopathies, where reduced UBE3A levels can lead to an enhanced rate of aggregate formation and cell death. Here, we review the literature on UBE3A in neurodevelopment, function, and neurodegenerative diseases and demonstrate that UBE3A could play a critical role in disease progression and cognitive function. [ABSTRACT FROM AUTHOR]

Background: Infertility is a reproductive health problem that attracts worldwide attention. Polycystic ovary syndrome (PCOS) is a major cause of female infertility and patients with obesity and PCOS are particularly common in clinical practice. Long non-coding RNA (lncRNAs) are a functional core in cells that regulate gene expression, transcription, and chromatin modification processes, and participate in epigenetics, cell cycle, and cell differentiation. LncRNAs are assumed to play a role in the occurrence and development of PCOS; however, their specific mechanism of action remains to be elucidated. Methods: High-throughput sequencing technology has been used to sequence and analyze lncRNAs in exosomes from the follicular fluid of patients with obesity and PCOS and those who underwent assisted reproductive therapy owing to male factors. Specific expression profiles of patients with obesity and PCOS were obtained and functional information analysis combined with a literature review were performed to screen for differentially expressed lncRNAs, which were validated using real-time reverse transcription quantitative polymerase chain reaction (RT-qPCR). Results: High-throughput sequencing analysis revealed that compared to normal patients with male infertility, patients with obesity and PCOS had a total of 20 lncRNAs with significant expression differences in follicular fluid exosomes. Among them, 17 lncRNAs were upregulated and three were downregulated. Functional analysis showed that differentially expressed genes were mainly enriched in "cell metabolism," "cell adhesion," and other aspects: related gene pathways mainly involved Huntington's disease, Parkinson's disease, spliceosomes, non-alcoholic fatty liver disease, and ribosomes. Verification of differentially expressed lncRNAs revealed that the expression of lncRNAs TPT1-AS1, PTOV1-AS1, PTPRG-AS1, and SNHG14 in follicular fluid exosomes was consistent with the sequencing results. Conclusion: A preliminary differential expression profile of lncRNAs in exosomes of patients with obesity and PCOS was established by transcriptomic analysis of these individuals. Our bioinformatics analysis results may be applicable to further study of the impact mechanism involving obesity and PCOS. These differentially expressed lncRNAs maybe served as potential biomarkers for in-depth studies of the occurrence, development on Follicle quality and function for patients with PCOS in the future. [ABSTRACT FROM AUTHOR]