Biology subjects

tatout, c.

Publications and source records attributed to tatout, c..

2 recordsLinked to original sources

bioRxiv2026

GH1-HMGA proteins restrict RNA-directed DNA methylation and antagonize linker histone H1 at euchromatic transposable elements

In plant genomes, transposable elements (TEs) are silenced by CG and non-CG DNA methylation, with non-CG methylation maintained by CMT chromomethylases and the RNA-directed DNA methylation (RdDM) pathway. In Arabidopsis, linker histone H1 differentially influences these pathways, as loss of H1 causes non-CG hypermethylation at pericentromeric TEs but hypomethylation at euchromatic TEs in gene-rich regions. The molecular basis of this antagonism has remained unclear. Here, we show that GH1-HMGAs, a family of H1-related High Mobility Group proteins, bind AT-rich sequences at euchromatic TEs and prevent RdDM-dependent non-CG methylation by limiting siRNA accumulation. Furthermore, GH1-HMGA and H1 compete for chromatin association at these TEs, as loss of GH1-HMGA triggers ectopic H1 redistribution, while loss of H1 increases GH1-HMGA enrichment, providing a mechanistic explanation for the non-CG hypomethylation observed in h1 mutants. Collectively, these findings reveal how GH1-HMGA proteins specifically restrain RdDM activity at euchromatic TEs and elucidate how the H1/GH1-HMGA balance spatially partitions distinct DNA methylation pathways across the genome.

genetics↗

bioRxiv2021

Evolutionary conserved protein motifs drive attachment of the plant nucleoskeleton at nuclear pores

The nucleoskeleton forms a filamentous meshwork under the nuclear envelope and contributes to the regulation of nuclear morphology and gene expression. To understand how the Arabidopsis nucleoskeleton physically connects to the nuclear periphery, we investigated the nucleoskeleton protein KAKU4 and sought for functional regions responsible for its localization at the nuclear periphery. Computational predictions identified three evolutionary conserved peptide motifs within the N-terminal region of KAKU4. Functional analysis revealed that these motifs are required for homomerization of KAKU4, interaction with the nucleoskeleton proteins CROWDED NUCLEI (CRWN) and localization at the nuclear periphery. We find that similar protein motifs are present in NUP82 and NUP136, two plant specific nucleoporins from the Nuclear Pore Complex (NPC) basket. These conserved motifs allow the two nucleoporins to bind CRWN proteins, thus revealing a physical link between the nucleoskeleton and nuclear pores in plants. Finally, whilst NUP82, NUP136 and KAKU4 have a common evolutionary history predating non-vascular land plants, KAKU4 mainly localizes outside the NPC suggesting neofunctionalization of an ancient nucleoporin into a new nucleoskeleton component.

genetics↗