Biology subjects

Steiner, F. A.

Publications and source records attributed to Steiner, F. A..

5 recordsLinked to original sources

bioRxiv2025

Transgenerational maintenance of H3K27me3 heterochromatin is balanced by chromodomain proteins in Caenorhabditis elegans

The ability to replicate and pass information to descendants is a fundamental requirement for life. In addition to the DNA-based genetic information, modifications of the DNA or DNA-associated proteins can create patterns of heritable gene regulation. Such epigenetic inheritance allows for adaptation without mutation, but its limits and regulation are incompletely understood. Here we developed a C. elegans system to study the transgenerational epigenetic inheritance of H3K27me3, a conserved histone posttranslational modification associated with gene repression. We find that induced alterations of the genome-wide H3K27me3 landscape and the associated fertility defects persist for many generations in genetically wildtype descendants under selective pressure. We uncover that the inheritance of the altered H3K27me3 landscape is regulated by two chromodomain proteins with antagonizing functions, and provide mechanistic insight into how this molecular memory is initiated and maintained. Our results demonstrate that epigenetic inheritance can act as a mutation-independent, heritable mechanism of adaptation. In BriefOzdemir et al. demonstrate that an altered genomic distribution of the histone modification H3K27me3 can be epigenetically inherited across many generations through the activity of HERI-1/SET-32/MES-4, which is antagonized by CEC-6/PRC2 in C. elegans. HighlightsO_LIAltered H3K27me3 landscapes can be inherited for at least 15 generations in C. elegans. C_LIO_LIThe chromodomain proteins CEC-6 and HERI-1 have opposite roles in antagonizing or promoting the maintenance of the altered H3K27me3 landscape. C_LIO_LIH3K23me3 and H3K36me3 replace H3K27me3 to promote the intergenerational and transgenerational inheritance of the altered epigenome. C_LI

genetics↗

bioRxiv2022

Recurrent but short-lived duplications of centromeric proteins in holocentric Caenorhabditis species

Centromeric histones (CenH3s) are essential for chromosome inheritance during cell division in most eukaryotes. CenH3 genes have rapidly evolved and undergone repeated gene duplications and diversification in many plant and animal species. In Caenorhabditis, two independent duplications of CenH3 (named hcp-3 for HoloCentric chromosome-binding Protein 3) have been previously identified: in C. elegans and C. remanei. Here, using phylogenomic analyses in Caenorhabditis, we find strict retention of the ancestral hcp-3 gene and eight additional independent hcp-3 duplications, most of which are only found in one or two species. hcp-3L (hcp-3-like) paralogs are expressed in both sexes (males and females/ hermaphrodites) and have a conserved histone fold domain. We identified novel N-terminal protein motifs, including putative kinetochore protein-interacting motifs and a potential separase cleavage site, which are well-conserved across Caenorhabditis HCP-3 proteins. Other N-terminal motifs vary in their retention across paralogs or species, revealing potential sub-functionalization or functional loss following duplication. C. afra encodes an unprecedented protein fusion, where the hcp-3 paralog fused to duplicated segments from hcp-4 (nematode CENP-C). Extending our analyses beyond CenH3, we found gene duplications of six inner and outer kinetochore genes in Caenorhabditis, including co-retention of different kinetochore protein paralogs in a few species. Our findings suggest that centromeric protein duplications occur frequently in Caenorhabditis nematodes, are selectively retained under purifying selection but only for short evolutionary periods, then degenerate or are lost entirely. We hypothesize that unique challenges associated with holocentricity in Caenorhabditis may lead to this rapid revolving door of kinetochore protein paralogs.

evolutionary biology↗

bioRxiv2021

Mitotic chromosome condensation requires phosphorylation of the centromeric protein KNL-2 in C. elegans

Centromeres are chromosomal regions that serve as sites for kinetochore formation and microtubule attachment, processes that are essential for chromosome segregation during mitosis. Centromeres are almost universally defined by the histone variant CENP-A. In the holocentric nematode C. elegans, CENP-A deposition depends on the loading factor KNL-2. Depletion of either CENP-A or KNL-2 results in defects in centromere maintenance, chromosome condensation and kinetochore formation, leading to chromosome segregation failure. Here, we show that KNL-2 is phosphorylated by CDK-1, and that mutation of three C-terminal phosphorylation sites causes chromosome segregation defects and an increase in embryonic lethality. In strains expressing phosphodeficient KNL-2, CENP-A and kinetochore proteins are properly localised, indicating that the role of KNL-2 in centromere maintenance is not affected. Instead, the mutant embryos exhibit reduced mitotic levels of condensin II on chromosomes and significant chromosome condensation impairment. Our findings separate the functions of KNL-2 in CENP-A loading and chromosome condensation and demonstrate that KNL-2 phosphorylation regulates the cooperation between centromeric regions and the condensation machinery in C. elegans. SUMMARY STATEMENTPhosphorylation of the essential centromere protein KNL-2 is required for mitotic chromosome condensation, but not for the role of KNL-2 in centromere maintenance and kinetochore formation.

cell biology↗

bioRxiv2019

Loss of histone H3.3 results in DNA replication defects and altered origin dynamics in C. elegans

Histone H3.3 is a replication-independent variant of histone H3 with important roles in development, differentiation and fertility. Here we show that loss of H3.3 results in replication defects in Caenorhabditis elegans embryos. To characterize these defects, we adapt methods to determine replication timing, map replication origins, and examine replication fork progression. Our analysis of the spatiotemporal regulation of DNA replication shows that despite the very rapid embryonic cell cycle, the genome is replicated from early and late firing origins and is partitioned into domains of early and late replication. We find that under temperature stress conditions, additional replication origins become activated. Moreover, loss of H3.3 results in impaired replication fork progression around origins, which is particularly evident at stress-activated origins. These replication defects are accompanied by replication checkpoint activation, a prolonged cell cycle, and increased lethality in checkpoint-compromised embryos. Our comprehensive analysis of DNA replication in C. elegans reveals the genomic location of replication origins and the dynamics of their firing, and uncovers a role of H3.3 in the regulation of replication origins under stress conditions.

genetics↗

bioRxiv2019

Local inhibition of PRC2 activity by H3.3K27M drives DNA replication defects through misregulation of the JNK pathway

Substitution of lysine 27 with methionine in histone H3.3 is a recently discovered driver mutation of pediatric high-grade gliomas. Mutant tumor cells show decreased levels and altered distribution of H3K27me3. How these chromatin changes are established genome-wide and lead to tumorigenesis only in specific tissues remains unclear. Here we show that H3.3K27M-mediated alterations in H3K27me3 distribution result in ectopic DNA replication and cell cycle progression of germ cells in Caenorhabditis elegans. By genetically inducing changes in the H3.3 distribution, we demonstrate that both H3.3K27M oncohistone incorporation and pre-existing H3K27me3 act locally and antagonistically on Polycomb Repressive Complex 2 (PRC2) in a concentration-dependent manner, explaining the observed H3K27me3 distribution in mutant cells. The altered heterochromatin patterns lead to extensive misregulation of gene expression. Through unbiased genetic screening, we found that inhibiting JNK pathway components, which are overexpressed in H3.3K27M cells, suppresses the ectopic DNA replication and cell cycle progression without rescuing the altered H3K27me3 distribution. Moreover, we show that JNK inhibition suppresses the replicative fate in human tumor-derived H3.3K27M cells, thus establishing C. elegans as a powerful model for the identification of potential drug targets for treatment of H3.3K27M tumors.

molecular biology↗