Biology subjects

Sia, Y.

Publications and source records attributed to Sia, Y..

3 recordsLinked to original sources

bioRxiv2026

J-domain proteins stimulate PKL-mediated chromatin compaction at H3K4-hypomethylated genomic loci

Chromatin accessibility varies widely across distinct genomic regions in eukaryotes, yet the mechanisms governing these differential patterns remain poorly understood. Here, we identify a subfamily of functionally redundant J-domain proteins (JDPs) that assemble into a protein complex with PICKLE (PKL), an evolutionarily conserved CHD3-type chromatin remodeler, in Arabidopsis thaliana. JDPs are required not only for maintaining PKL protein stability but also for stimulating its nucleosome remodeling and ATPase activities. A previously uncharacterized histone-binding domain (HBD) within JDPs specifically recognizes the N-terminal tail of histone H3 when the H3K4me3 modification is absent. This interaction enhances PKL-mediated nucleosome sliding and ATPase activities in vitro, and promotes PKL-dependent chromatin compaction at H3K4me3-depleted genomic loci in vivo. The PKL-JDP complex drives chromatin compaction to repress developmentally regulated genes, thereby governing key developmental phase transitions, including the embryo-to-seedling transition and flowering. Collectively, these findings uncover a distinct mechanism by which the absence of H3K4me3 is sensed to initiate regional chromatin compaction, repress developmentally regulated genes, and facilitate key developmental transitions.

plant biology↗

bioRxiv2025

A Complete Telomere-to-Telomere Diploid Reference Genome for Indian Population

Human reference genomes have been instrumental in advancing genomic and biomedical research, but South and Southeast Asian populations are underrepresented, despite accounting for a large proportion of world population. As a part of effort on generating reference genomes for these populations, we present the first gapless, telomere-to-telomere (T2T) diploid genome assembly created by using a trio sample set of Indian ancestry (I002C), with NG50 of 154.89 Mb and 146.27 Mb for the maternal and paternal haplotypes, including the fully assembled rDNA array for the maternal chromosome 21 and Y chromosome. With the Merqury QVs of 82.05, 83.08 and 82.64 for the maternal, paternal and haploid assemblies respectively, I002C represents the highest-quality human genome assembled in both diploid and haploid forms to date. Compared to CHM13, the I002C genome displays substantial sequence diversity, resulting in 14,943 structural variants, including 3,236 novel variants absent from public databases. Analysis of trio-phased haplotypes further revealed elevated inter-haplotype divergence within centromeric and subtelomeric regions, along with identification of differentially methylated regions (DMRs) as candidates for novel imprinting loci. As a result of substantial SVs between them, I002C is a more suitable reference than CHM13 for the genomic analysis of South Asian samples with less reference bias and better performance in mapping and variant calling, particularly for long read sequencing data. As the first high-quality T2T diploid reference genome for Indian, the largest worlds population, I002C contributes to the growing set of population-specific reference genomes and helps to overcome a significant gap in human genome diversity.

genomics↗

bioRxiv2023

Structure of the ISW1a complex bound to the dinucleosome

Nucleosomes are basic repeating units of chromatin, and form regularly spaced arrays in cells. Chromatin remodelers alter the positions of nucleosomes, and are vital in regulating chromatin organization and gene expression. Here we report the cryoEM structure of chromatin remodeler ISW1a complex bound to the dinucleosome. Each subunit of the complex recognizes a different nucleosome. The motor subunit binds to the mobile nucleosome and recognizes the acidic patch through two arginine residues, and the DNA-binding module interacts with the entry DNA at the nucleosome edge. This nucleosome-binding mode provides the structural basis for linker DNA sensing of the motor. Notably, the Ioc3 subunit recognizes the disk face of the adjacent nucleosome through the H4 tail, the acidic patch and the nucleosomal DNA, which is important for the spacing activity in vitro, and for nucleosome organization and cell fitness in vivo. Together, these findings support the nucleosome spacing activity of ISW1a, and add a new mode of nucleosome remodeling in the context of a chromatin environment.

biochemistry↗