Biology subjects

Gray, S. J.

Publications and source records attributed to Gray, S. J..

2 recordsLinked to original sources

bioRxiv2025

Dimerization of Cdc13 is essential for dynamic DNA exchange on telomeric DNA

Single-stranded DNA (ssDNA) binding proteins (ssBPs) are essential in eukaryotes to protect telomeres from nuclease activity. In Saccharomyces cerevisiae, the ssBP Cdc13 is an essential protein that acts as a central regulator of telomere length homeostasis and chromosome end protection, both alone and as part of the Cdc13-Stn1-Ten1 (CST) complex. Cdc13 has high binding affinity for telomeric ssDNA, with a very slow off-rate. Previously, we reported that despite this tight ssDNA binding, Cdc13 rapidly exchanges between bound and unbound telomeric ssDNA substrates, even at sub-stoichiometric concentrations of competitor ssDNA. This dynamic DNA exchange (DDE) is dependent on the presence and length of telomeric repeat sequence ssDNA and requires both Cdc13 DNA binding domains, OB1 and OB3. Here we investigated if Cdc13 dimerization is important for DDE by characterizing the dimerization mutant Cdc13-L91R. Using mass photometry, we confirmed that Cdc13-L91R fails to dimerize in solution, even in the presence of ssDNA. Gel-based DDE assays revealed that Cdc13-L91R fails to undergo ssDNA exchange compared to recombinant wild-type protein. Biolayer interferometry demonstrated that this effect was not due to differences in ssDNA binding kinetics. Thus, dimerization of Cdc13 is essential for DDE, and we model how this may impact telomere biology in vivo. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=90 SRC="FIGDIR/small/645294v1_ufig1.gif" ALT="Figure 1"> View larger version (22K): org.highwire.dtl.DTLVardef@18f34fdorg.highwire.dtl.DTLVardef@e00e71org.highwire.dtl.DTLVardef@1d4400aorg.highwire.dtl.DTLVardef@1b87a7e_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2025

In vitro cellular phenotypes of cortical neurons from R255X MECP2 knock-in mice are improved by either expression of wildtype MeCP2 or read-through with G418

Approximately 60% of individuals with Rett syndrome (RTT) carry a nonsense variant in the MECP2 gene; thus, there is an unmet need to identify novel nonsense suppression compound(s) that can restore full length MeCP2 protein levels and function. Here, we characterized neuronal phenotypes in cultured cortical neurons from newborn knock-in mice harboring the MECP2 R255X variant. After 2 weeks in vitro, R255X mutant neurons showed smaller cell bodies, shorter dendrites, fewer dendritic branches, and a lower density of excitatory synapses when compared to wildtype (WT) neurons. Transduction of AAV9-MeCP2-GFP in R255X mutant neurons made these cellular phenotypes similar to those in WT neurons, including soma size, dendritic length and branching, and excitatory synapse density. As proof of principle for the potential clinical use of read-through compounds, cultured R255X mutant neurons treated with the aminoglycoside G418 for 72h in vitro showed cell body size and excitatory synapse density similar to WT neurons. We expect these combined approaches will identify effective compounds to suppress translation termination at a premature termination codon, which can be moved to further preclinical functional and behavioral studies in R255X MECP2 knock-in mice. Summary StatementExpression of wildtype MECP2 or treatment with G418 in vitro restored cell body size, dendritic length, and dendritic spine density in cortical neurons from R255X MECP2 knock-in mice to levels comparable to wildtype neurons.

neuroscience↗