Biology subjects

Martin, C. J.

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

5 recordsLinked to original sources

bioRxiv2026

Hat1 Orchestrates Heterochromatin Inheritance by Regulating Localization of H3K9 Methyltransferases

Many regions of heterochromatin associate with the nuclear periphery and are known as Lamin-associated domains (LADs). Histone acetyltransferase 1 (Hat1) is a highly conserved enzyme which acetylates newly synthesized histones H4 on lysines 5 and 12 prior to their deposition on chromatin. Hat1 is required to preserve chromatin accessibility within a subset of LADs called Hat1-dependent accessibility domains (HADs). Here we profile a diverse set of histone modifications in Hat1 KO and WT immortalized mouse embryonic fibroblasts (iMEFs) and find that Hat1 regulates diverse aspects of the structure of HADs and non-HAD LADs (nhLADS). In HADs, these changes include the conversion of H3K9me2 to H3K9me3. Analysis of H3K9-specific histone methyltransferases (HMTs) shows that that Suv39h1 and Suv39h2 have distinct localization patterns, where only Suv39h2 localizes to LADs. G9a only localizes to LADs in regions enriched for H3K9me2. We find that Hat1 loss results in a redistribution of these HMTs in both HADs and nh LADs. There is a decrease in the levels of G9a with a concomitant increase in Suv39h2. These results suggest Hat1 functions to restrain the formation of a more strongly heterochromatic state and highlight a role for Hat1 as an essential regulator of heterochromatin inheritance. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=97 SRC="FIGDIR/small/713225v1_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@9f6238org.highwire.dtl.DTLVardef@1e95415org.highwire.dtl.DTLVardef@18f3e0aorg.highwire.dtl.DTLVardef@1322426_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2026

HAT1 Regulates Intestinal Stem Cell Proliferation and Differentiation

Stem cells are critical for the development and maintenance of tissue integrity. An important example is intestinal stem cells (ISCs) that generate all epithelial cell types necessary for formation of the intestinal lining. HAT1, a histone acetyltransferase that acetylates newly synthesized histone H4 molecules on lysine residues 5 and 12 during replication-coupled chromatin assembly, is specifically expressed in intestinal stem and progenitor cells located in intestinal crypts. To determine if HAT1 is important for intestinal stem and progenitor cell function, we generated an inducible deletion of the HAT1 gene in intestinal epithelial cells. Loss of HAT1 resulted in morphological defects in the proximal end of the small intestine. Following loss of HAT1, intestinal crypts became elongated, with an increase in stem and progenitor cell proliferation and an increase in the population of OLFM+ cells. Loss of HAT1 also resulted in alterations in intestinal stem cell differentiation, including an increase in the number of Goblet cells and the mislocalization of Paneth cells into villi. HAT1 is specifically responsible for the acetylation of histone H4 lysine 5 (H4K5ac) in intestinal stem cells. Genome-wide characterization of HAT1-dependent H4K5ac in intestinal crypt cells indicates that the most significant loss of H4K5ac occurs in lamina-associated domains (LADs). Loss of H4K5ac in LADs is accompanied by an increase in histone H3 K9 tri-methylation indicating that HAT1 regulates LAD chromatin structure in intestinal crypt cells. A direct role for HAT1 in intestinal stem cell function was demonstrated using organoids in culture. HAT1 is required for differentiation in organoids and for the maintenance of Lgr5+ stem cells. These results indicate that HAT1 is required for the proper regulation of intestinal stem cell renewal and differentiation.

cell biology↗

bioRxiv2025

Spatio-temporal protein interaction analysis using bimolecular fluorescence complementation in C. elegans

Dynamic protein-protein interactions (PPIs) shape all aspects of cellular biology. Thus, significant efforts have been made to develop assays testing binary PPIs. The transparency of C. elegans makes it a great model organism for fluorescence-based PPI detection in vivo. However, to date, there is currently a lack of quantitative PPI assays that also provide information on the subcellular location of protein interactions in C. elegans. Here, we have made several modifications to the original bimolecular fluorescence complementation (BiFC) assay used in C. elegans to make it more quantitative and spatio-temporally controlled. First, transgenes are expressed at single copy, reducing the variability associated with multi-copy expression. Second, we have added bicistronic reference fluorescent proteins to each transgene, allowing for the normalization and quantification of the PPI. Finally, we have incorporated the auxin-inducible degradation system, allowing for small-molecule inducible control of the PPI signal. We demonstrate the utility of our modified BiFC assay by testing several model PPIs. Thus, we anticipate that our updated BiFC approach will expand the available tools for studying PPIs in C. elegans, but similar logic could be applied to other model organisms amenable to transgenesis and in vivo fluorescent imaging. Article SummaryProtein-protein interactions (PPIs) play a central role in all facets of cellular biology. Here, we developed an improved assay to study PPIs in C. elegans, based on bimolecular fluorescence complementation (BiFC), where two halves of split-YFP can be reconstituted in an interaction-dependent manner. Our modifications include making the readout of the assay less variable and more quantitative, while also enabling signal to accumulate in an inducible manner. We envision that our updated BiFC approach will serve as a useful tool for C. elegans researchers interested in characterizing PPIs of interest in vivo.

molecular biology↗

bioRxiv2024

Distinct Classes of Lamin-Associated Domains are Defined by Differential Patterns of Repressive Histone Methylation

A large fraction of the genome interacts with the nuclear periphery through lamina-associated domains (LADs), repressive regions which play an important role in genome organization and gene regulation across development. Despite much work, LAD structure and regulation are not fully understood, and a mounting number of studies have identified numerous genetic and epigenetic differences within LADs, demonstrating they are not a uniform group. Here we profile Lamin B1, HP1{beta}, H3K9me3, H3K9me2, H3K27me3, H3K14ac, H3K27ac, and H3K9ac in MEF cell lines derived from the same mouse colony and cluster LADs based on the abundance and distribution of these features across LADs. We find that LADs fall into 3 groups, each enriched in a unique set of histone modifications and genomic features. Each group is defined by a different heterochromatin modification (H3K9me3, H3K9me2, or H3K27me3), suggesting that all three of these marks play important roles in regulation of LAD chromatin and potentially of lamina association. We also discover unique features of LAD borders, including a LAD border-specific enrichment of H3K14ac. These results reveal important distinctions between LADs and highlight the rich diversity and complexity in LAD structure and regulatory mechanisms.

genomics↗

bioRxiv2018

Concurrent infection with Mycobacterium tuberculosis confers robust protection against secondary infection in macaques

Introduction Introduction Main text Methods References For many pathogens, including most targets of effective vaccines, infection elicits an immune response that confers significant protection against reinfection. There has been significant debate as to whether natural M. tuberculosis (Mtb) infection confers protection against reinfection. Here we experimentally assessed the protection conferred by concurrent Mtb infection in macaques, a robust experimental model of human tuberculosis (TB), using a combination of serial imaging and Mtb challenge strains differentiated by DNA identifiers. Strikingly, ongoing Mtb infection provided complete protection against establishment of secondary infection in over half of the macaques and allowed near sterilizing bacterial control for those in which a secondary infection was established. By contrast, boosted B ...

microbiology↗