Biology subjects

Ausio, J.

Publications and source records attributed to Ausio, J..

8 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↗

bioRxiv2025

Methionine regulates antitumor function of CD8⁺ T cells through polyamine synthesis

Methionine is an essential amino acid critical for T cell activation. While methionine restriction (MR) combined with immune checkpoint blockade has been shown to enhance T cell function, the impact of methionine on adoptive T cell therapies is largely unexplored. Here, we examined the functionality of T cells under MR and pharmaceutical inhibition of the methionine cycle (MAT2Ai), using primary T cells and a murine adoptive T cell therapy model. In vitro, transient MR or MAT2Ai treatment increased interferon gamma (IFN{gamma}) expression in CD8+ T cells, whereas sustained MR led to the upregulation of T cell exhaustion-associated markers. Mechanistically, transient MR suppressed the polyamine synthesis pathway, and supplementation with polyamines reversed MR-induced IFN{gamma} expression. Genetic ablation of s-adenosylmethionine decarboxylase, an enzyme in the polyamine synthesis pathway, recapitulated the effect of MR, indicating that transient MR enhances T cell function by inhibiting polyamine synthesis. Despite this, transient MR treatment of ovalbumin (OVA)-specific (OT-I) CD8+ T cells prior to adoptive transfer did not improve antitumor efficacy against EG7-OVA tumors in vivo. In contrast, sustained dietary MR accelerated EG7-OVA tumor growth in mice treated with OT-I T cells, demonstrating that methionine availability is essential for the activity of adoptively transferred T cells. These findings suggest that enhancing methionine availability in the tumor microenvironment may improve the efficacy of adoptive T cell therapies.

immunology↗

bioRxiv2024

Human MeCP2 binds to promoters and inhibits transcription in an unmethylated S. cerevisiae genome

MeCP2 is a DNA-binding transcriptional regulator that is present at near-histone levels in mammalian cortical neurons. Originally identified as a DNA methylation reader, MeCP2 has been proposed to repress transcription by recruiting corepressors to methylated DNA. While some genome-wide occupancy studies support a preference for methylated DNA, others suggest that MeCP2 binding is more influenced by DNA sequence and accessibility than methylation status. Moreover, multiple studies also suggest a role for MeCP2 in gene activation. To clarify MeCP2 function we expressed MeCP2 in Saccharomyces cerevisiae, which lacks DNA methylation and known MeCP2 corepressors. We find that MeCP2 is toxic to yeast and globally inhibits transcription, indicating that MeCP2 can have significant functional impacts without DNA methylation or mammalian corepressors. A subset of MeCP2 mutations that cause the neurodevelopmental disorder Rett syndrome, particularly those that map to the DNA binding domain, alleviate the toxicity of MeCP2 in yeast. Consistent with the importance of DNA binding for toxicity in yeast, we show that MeCP2 binds to the yeast genome, with increased occupancy at GC-rich, nucleosome-depleted sequences. These findings present yeast as a useful tool for analyzing MeCP2 and reveal MeCP2 properties that are not strictly dependent on DNA methylation or mammalian corepressors. SummaryMeCP2, a transcription regulator found in vertebrates, is proposed to repress transcription by recruiting corepressors to methylated DNA. In this work Brown et al. show that MeCP2 expressed in Saccharomyces cerevisiae, which lacks DNA methylation and mammalian co-repressors, binds promoters and inhibits transcription. A subset of MeCP2 mutations that cause the neurodevelopmental disorder, Rett syndrome, rescues MeCP2-induced phenotypes in yeast, supporting the relevance of these results to MeCP2 function in mammals.

molecular biology↗

bioRxiv2024

The protamines of the noble false widow spider Steatoda nobilis provide an example of liquid-liquid phase separation chromatin transitions during spermiogenesis

While there is extensive information about sperm nuclear basic proteins (SNBP) in vertebrates, there is very little information about Arthropoda by comparison. This paper aims to contribute to filling this gap by analyzing these proteins in the sperm of the noble false widow spider Steatoda nobilis (Order Araneae, Family Theridiidae). To this end, we have developed a protein extraction method that allows the extraction of cysteine-containing protamines suitable for the preparation and analysis of SNBPs from samples where the amount of starting tissue material is limited. We carried out top-down mass spectrometry sequencing and molecular phylogenetic analyses to characterize the protamines of S. nobilis and other spiders. We also used electron microscopy to analyze the chromatin organization of the sperm, and we found it to exhibit liquid-liquid phase spinodal decomposition during the late stages of spermiogenesis. These studies further our knowledge of the distribution of SNBPs within the animal kingdom and provide additional support for a proposed evolutionary origin of many protamines from a histone H1 (H5) replication-independent precursor.

biochemistry↗

bioRxiv2021

Fundamental Role Of The H2A.Z C-Terminal Tail In The Formation Of Constitutive Heterochromatin

H2A.Z-nucleosomes are present in both euchromatin and heterochromatin and it has proven difficult to interpret their disparate roles in the context of their stability features. Using an in situ assay of nucleosome stability and DT40 cells expressing engineered forms of the histone variant we show that native H2A.Z, but not C-terminally truncated H2A.Z (H2A.Z{Delta}C), is released from nucleosomes of peripheral heterochromatin at unusually high salt concentrations. H2A.Z and H3K9me3 landscapes are reorganized in H2A.Z{Delta}C-nuclei and overall sensitivity of chromatin to nucleases is increased. These tail-dependent differences are recapitulated upon treatment of HeLa nuclei with the H2A.Z-tail-peptide (C9), with MNase sensitivity being increased at specific regions including promoters. Introduced into live cells C9 elicits down-regulation of [~]560 genes with nonrandom chromosomal band-localization and pathway-spectrum. Thus, tail-dependent heterogeneity of H2A.Z-nucleosomes is revealed at all organization levels of chromatin and epigenetic modulation can be achieved by targeting molecular interactions involving its C-terminal tail.

cell biology↗

bioRxiv2018

MeCP2-E1 isoform is a dynamically expressed, weakly DNA-bound protein with different protein and DNA interactions compared to MeCP2-E2

MeCP2 - a chromatin-binding protein associated with Rett syndrome - has two main isoforms, MeCP2-E1 and MeCP2-E2, with 96% amino acid identity differing in a few N-terminal amino acid residues. Previous studies have shown brain region-specific expression of these isoforms which, in addition to their different cellular localization and differential expression during brain development, suggest they may also have non-overlapping molecular mechanisms. However, differential functions of MeCP2-E1 and E2 remain largely unexplored. Here, we show that the N-terminal domains (NTD) of MeCP2-E1 and E2 modulate the ability of the methyl binding domain (MBD) to interact with DNA as well as influencing the turnover rates, binding dynamics, response to nuclear depolarization, and circadian oscillations of the two isoforms. Our proteomics data indicate that both isoforms exhibit unique interacting protein partners. Moreover, genome-wide analysis using ChIP-seq provide evidence for a shared as well as a specific regulation of different sets of genes. Our findings provide insight into the functional complexity of MeCP2 by dissecting differential aspects of its two isoforms.\n\nSignificanceWhether the two E1 and E2 isoforms of MeCP2 have different structural and/or functional implications has been highly controversial and is not well known. Here we show that the relatively short N-terminal sequence variation between the two isoforms impinges them with an important DNA binding difference. Moreover, MeCP2-E1 and E2 exhibit a different cellular dynamic behavior and have some distinctive interacting partners. In addition, while sharing genome occupancy they specifically bind to several distinctive genes.

biochemistry↗

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↗

bioRxiv2017

The role of N-terminal modification of MeCP2 in the pathophysiology of Rett syndrome

Methyl CpG-binding protein 2 (MeCP2), the mutated protein in Rett syndrome (RTT), is a crucial chromatin-modifying and gene-regulatory protein that has two main isoforms (MeCP2_E1 and MeCP2_ E2) due to the alternative splicing and switching between translation start codons in exons one and two. Functionally, these two isoforms appear to be virtually identical; however, evidence suggests that only MeCP2_E1 is relevant to RTT, including a single RTT missense mutation in exon 1, p.Ala2Val. Here, we show that N-terminal co- and post- translational modifications differ for MeCP2_E1, MeCP2_E1-p.Ala2Val and MeCP2_E2, which result in different protein degradation rates in vitro. We report partial N-methionine excision (NME) for MeCP2_E2, whereas NME for MeCP2_E1 is complete. Surprisingly, we also observed evidence of excision of multiple alanine residues from the N-terminal polyalanine stretch. Regarding MeCP2_E1-Ala2Val, we also observed only partial NME and N-acetylation (NA) of either methionine or valine. The localization of MeCP2_E1 and co-localization with chromatin appear to be unaffected by the p.Ala2Val mutation. However, a higher proteasomal degradation rate was observed for MeCP2_E1-Ala2Val compared with that for wild type (WT) MeCP2_E1. Thus, the etiopathology of p.Ala2Val is likely due to a reduced bio-availability of MeCP2 because of the faster degradation rate of the unmodified defective protein. MeCP2_E1 is thought to have a much higher translational efficiency than MeCP2_E2. Our data suggest that this increased efficiency may be balanced by a higher degradation rate. The higher turnover rate of the MeCP2_E1 protein suggests that it may play a more dynamic role in cells than MeCP2_E2.\n\nSignificance statementThe Rett syndrome protein, MeCP2, undergoes a number of modifications before becoming functionally active in the bodys cells. Here, we report the presence of N-terminal modifications in both MeCP2 isoforms, MeCP2_E1 and MeCP2_E2, and that the only reported Rett missense mutation in exon 1, p.Ala2Val, disrupts these modifications, decreasing the longevity of the protein. Interestingly, p.Ala2Val mutations have been reported in many other disease genes, such as DKCX, ECHS1, IRF6, SMN1, and TNNI3, and the etiopathological mechanism(s) have never been explained. Thus, this work is important not only for the understanding of the pathophysiology of Rett syndrome but also for a deeper understanding of the effects of genetic mutations at the N-terminal end of genes in general.

genetics↗