Biology subjects

Nelson, C. J.

Publications and source records attributed to Nelson, C. J..

7 recordsLinked to original sources

bioRxiv2025

MeCP2 NID interaction with RNA: Implications for Rett Syndrome-Relevant Protein Regulation

Mutations in the MECP2 gene cause the progressive neurodevelopmental disorder Rett syndrome. Pathogenic missense mutation hotspots exist in the proteins Methyl DNA binding Domain (MBD), and the NCoR Interaction Domain (NID), indicating these regions as critical for MeCP2 function. The NID binds to a co-repressor complex allowing transcriptional repression at target genes. A putative RNA Binding Domain (RBD) was identified that overlaps with the NID, yet the role that RNA interaction plays in MeCP2 function remains underexplored. Using cell-based and in vitro molecular assays, we validated RNA interaction at the NID/RBD of MeCP2 both to a dsRNA probe in vitro and to the lncRNA NEAT1_2 in cells. As expected, this region did not appear to affect MeCP2-chromatin interactions; however, we found that RNA-RBD interaction precludes MeCP2-NCoR binding in cells. Taken together, we find that RNA interaction at this non-canonical RNA binding domain regulates important MeCP2-protein interactions and therefore may be a key part of the pathophysiology of Rett syndrome.

molecular biology↗

bioRxiv2023

Intrinsic disorder specifies discreet functions of nucleoplasmin-like histone chaperones

Nucleoplasmin (NPM) histone chaperones regulate distinct processes in the nucleus and nucleolus. While intrinsically disordered regions (IDRs) are hallmarks of NPMs, it is not clear if all NPM functions require these unstructured features. We assessed the importance of IDRs in yeast NPM-like proteins and found that regulation of rDNA copy number, and genetic interactions with the nucleolar RNA surveillance machinery require the highly conserved FKBP prolyl isomerase domain, but not the NPM domain or IDRs. By contrast, transcriptional silencing in the nucleus requires IDRs. We demonstrate that multiple lysines in poly-acidic serine/lysine motifs of IDRs are required for both lysine polyphosphorylation and NPM-mediated transcriptional silencing. These results demonstrate that NPM-like proteins do not rely on IDRs for all chromatin-related functions.

molecular biology↗

bioRxiv2023

Bridging Imaging Users to Imaging Analysis - A community survey

The "Bridging Imaging Users to Imaging Analysis" survey was conducted in 2022 by the Center for Open Bioimage Analysis (COBA), Bioimaging North America (BINA), and the Royal Microscopical Society Data Analysis in Imaging Section (RMS DAIM) to understand the needs of the imaging community. Through multi-choice and open-ended questions, the survey inquired about demographics, image analysis experiences, future needs, and suggestions on the role of tool developers and users. Participants of the survey were from diverse roles and domains of the life and physical sciences. To our knowledge, this is the first attempt to survey cross-community to bridge knowledge gaps between physical and life sciences imaging. Survey results indicate that respondents overarching needs are documentation, detailed tutorials on the usage of image analysis tools, user-friendly intuitive software, and better solutions for segmentation, ideally in a format tailored to their specific use cases. The tool creators suggested the users familiarize themselves with the fundamentals of image analysis, provide constant feedback, and report the issues faced during image analysis while the users would like more documentation and an emphasis on tool friendliness. Regardless of the computational experience, there is a strong preference for written tutorials to acquire knowledge on image analysis. We also observed that the interest in having office hours to get an expert opinion on their image analysis methods has increased over the years. In addition, the community suggests the need for a common repository for the available image analysis tools and their applications. The opinions and suggestions of the community, released here in full, will help the image analysis tool creation and education communities to design and deliver the resources accordingly.

scientific communication and education↗

bioRxiv2021

Cytoplasmic Switch of ARS2 Isoforms Promotes Nonsense-Mediated mRNA Decay and Arsenic Sensitivity

The life of RNA polymerase II (RNAPII) transcripts is shaped by the dynamic formation of mutually exclusive ribonucleoprotein complexes (RNPs) that direct transcript biogenesis and turnover. A key regulator of RNA metabolism in the nucleus is the scaffold protein ARS2 (arsenic resistance protein 2), bound to the cap binding complex (CBC). We report here that alternative splicing of ARS2s intron 5, generates cytoplasmic isoforms that lack 270 amino acids from the N-terminal of the protein and are functionally distinct from nuclear ARS2. Switching of ARS2 isoforms within the CBC in the cytoplasm has dramatic functional consequences, changing ARS2 from a NMD inhibitor to a NMD promoter that enhances the binding of UPF1 to NCBP1, ERF1 and DHX34, favouring SURF complex formation, SMG7 recruitment and transcript degradation. ARS2 isoform exchange is also relevant during arsenic stress, where cytoplasmic ARS2 promotes a global response to arsenic in a CBC-independent manner. We propose that ARS2 isoform switching promotes the proper recruitment of RNP complexes during NMD and the cellular response to arsenic stress. The existence of non-redundant ARS2 isoforms is relevant for cell homeostasis, stress response, and cancer treatment.

molecular biology↗

bioRxiv2019

Genetic dissection of the redundant and divergent functions of histone chaperone paralogs in yeast

Gene duplications increase organismal robustness by providing freedom for gene divergence or by increasing gene dosage. The yeast histone chaperones Fpr3 and Fpr4 are paralogs that can assemble nucleosomes in vitro, however the genomic locations they target and their functional relationship is poorly understood. We refined the yeast synthetic genetic array (SGA) approach to enable the functional dissection of gene paralogs. Applying this method to Fpr3 and Fpr4 uncovered their redundant and divergent functions: while Fpr3 is uniquely involved in chromosome segregation, Fpr3 and Fpr4 co-operate on some genes and are redundant on others where they impact gene expression and transcriptional processivity. We find that the TRAMP5 RNA exosome is essential in{Delta} fpr3{Delta}fpr4 yeast and leverage this information to identify Fpr3/4 target loci. Amongst these are the non-transcribed spacers of ribosomal DNA where either paralog is sufficient to establish chromatin that is both transcriptionally silent and refractory to recombination. These data provide evidence that Fpr3 and Fpr4 have shared chromatin-centric functions, especially at nucleolar rDNA. However, their distinct genetic interaction profiles show they also have evolved separate functions outside of the nucleolus.

genetics↗

bioRxiv2019

Hybrid optical gating for long-term 3D time-lapse imaging of the beating embryonic zebrafish heart

Three-dimensional fluorescence time-lapse imaging of structural, cellular and sub-cellular processes in the beating heart is an increasingly achievable goal using the latest imaging and computational techniques. However, previous approaches have had significant limitations. Temporarily arresting the heart using drugs disrupts the hearts physiological state, and the use of ultra-high frame-rates for fluorescence image acquisition causes phototoxic cell damage. Real-time triggered imaging, synchronized to a specific phase in the cardiac-cycle, can computationally "freeze" the heart to acquire the minimal number of fluorescence images required for 3D time-lapse imaging. However, until now no solution has been able to maintain phase-lock to the same point in the cardiac cycle for more than about one hour. Our new hybrid optical gating system maintains phase-lock for up to 24 h, acquiring synchronized 3D+time video stacks of the unperturbed heart in vivo. This approach has enabled us to observe detailed developmental, structural, cellular and subcellular processes, including live cell division and cell fate tracking, in the embryonic zebrafish heart using transgenic fish lines expressing cell-specific fluorophores. We show that our approach not only provides high spatial and temporal resolution 3D-imaging, but also avoids phototoxic injury, where alternative approaches induce measurable harm. This provides superb cellular and subcellular imaging of the heart while it is beating in its normal physiological state, and opens up new and exciting opportunities for further study in the heart and other moving cellular and subcellular structures in vivo.

bioinformatics↗

bioRxiv2018

A novel histone H4 variant regulates rDNA transcription in breast cancer

Histone variants, present in various cell types and tissues, are known to exhibit different functions. For example, histone H3.3 and H2A.Z are both involved in gene expression regulation, whereas H2A.X is a specific variant that responds to DNA double-strand breaks. In this study, we characterized H4G, a novel hominidae-specific histone H4 variant. H4G expression was found in a variety of cell lines and was particularly overexpressed in the tissues of breast cancer patients. H4G was found to localize primarily to the nucleoli of the cell nucleus. This localization was controlled by the interaction of the alpha helix 3 of the histone fold motif with the histone chaperone, nucleophosphomin 1. In addition, we found that H4G nucleolar localization increased rRNA levels, protein synthesis rates, and cell cycle progression. Furthermore, micrococcal nuclease digestion of H4G-containing nucleosomes reconstituted in vitro indicated that H4G destabilizes the nucleosome, which may serve to alter nucleolar chromatin in a way that enhances rDNA transcription in breast cancer tissues.

molecular biology↗