Biology subjects

Blundon, J.

Publications and source records attributed to Blundon, J..

3 recordsLinked to original sources

bioRxiv2024

Reduced Levels of Lagging Strand Polymerases Shape Stem Cell Chromatin

Stem cells display asymmetric histone inheritance while non-stem progenitor cells exhibit symmetric patterns in the Drosophila male germline lineage. Here, we report that components involved in lagging strand synthesis, such as DNA polymerase and {delta} (Pol and Pol{delta}), have significantly reduced levels in stem cells compared to progenitor cells. Compromising Pol genetically induces the replication-coupled histone incorporation pattern in progenitor cells to be indistinguishable from that in stem cells, which can be recapitulated using a Pol inhibitor in a concentration-dependent manner. Furthermore, stem cell-derived chromatin fibers display a higher degree of old histone recycling by the leading strand compared to progenitor cell-derived chromatin fibers. However, upon reducing Pol levels in progenitor cells, the chromatin fibers now display asymmetric old histone recycling just like GSC-derived fibers. The old versus new histone asymmetry is comparable between stem cells and progenitor cells at both S-phase and M-phase. Together, these results indicate that developmentally programmed expression of key DNA replication components is important to shape stem cell chromatin. Furthermore, manipulating one crucial DNA replication component can induce replication-coupled histone dynamics in non-stem cells in a manner similar to that in stem cells. One Sentence SummaryDelayed lagging strand synthesis regulates asymmetric histone incorporation.

developmental biology↗

bioRxiv2023

Skp1 proteins are structural components of the synaptonemal complex in C. elegans

The synaptonemal complex (SC) is a hallmark of meiotic prophase that plays a crucial role in regulating crossovers between homologous chromosomes. Here, we demonstrate that two Skp1-related proteins in C. elegans, SKR-1 and SKR-2, serve as structural components of the SC, independent of their canonical functions within the Skp1-Cul1-F-box (SCF) ubiquitin ligase complex. SKR-1 and SKR-2 localize to the central region of the SC, and synapsis requires their dimerization through a hydrophobic interface that overlaps with the binding sites for CUL-1 and F-box proteins. Using in vitro reconstitution and in vivo analysis of mutant proteins, we show that SKR proteins interact with the other SC proteins using their C-terminal helices to form a soluble complex, which likely represents a basic building block for SC assembly. Our findings demonstrate how conserved Skp1 proteins are repurposed as part of the SC and may provide insight into how synapsis is coupled to cell cycle progression.

cell biology↗

bioRxiv2021

The CHK-2 antagonizing phosphatase PPM-1.D regulates meiotic entry via catalytic and non-catalytic activities

The transition from the stem cell/progenitor fate to meiosis is mediated by several redundant post-transcriptional regulatory pathways in C. elegans. Interfering with all three branches causes tumorous germlines. SCFPROM-1 comprises one branch and mediates a scheduled degradation step at entry into meiosis. prom-1 mutants show defects in timely initiation of events of meiotic prophase I, resulting in high rates of embryonic lethality. Here, we identify the phosphatase PPM-1.D/Wip1 as crucial substrate for PROM-1. We report that PPM-1.D antagonizes CHK-2 kinase, a key regulator for meiotic prophase initiation e.g., DNA double strand breaks, chromosome pairing and synaptonemal complex formation. We propose that PPM-1.D controls the amount of active CHK-2 by both catalytic and non-catalytic activities, where strikingly the non-catalytic regulation seems to be crucial at meiotic entry. PPM-1.D sequesters CHK-2 at the nuclear periphery and programmed SCFPROM-1 mediated degradation of PPM-1.D liberates the kinase and promotes meiotic entry.

cell biology↗