Biology subjects

Aasland, R.

Publications and source records attributed to Aasland, R..

4 recordsLinked to original sources

bioRxiv2026

HP1α depletion and TGFβ activation exert antagonistic effects on 3D genome organization

The three-dimensional (3D) organization of the human genome plays a critical role in regulating gene expression and is frequently disrupted in cancer. However, how key factors like Heterochromatin Protein 1 alpha (HP1) and Transforming Growth Factor beta (TGF{beta}) remodel this architecture to drive tumorigenesis remains poorly understood. We investigated the effects of HP1 knockdown and TGF{beta} treatment on higher-order chromatin structure and gene expression in human mammary epithelial cells. Our findings reveal that HP1 depletion and TGF{beta} stimulation exert distinct and opposing effects on genome compartmentalization and sub compartmentalization. HP1 knockdown drives a genome-wide shift of chromatin from transcriptionally inactive B compartments to active A compartments. This is accompanied by a stepwise redistribution of A subcompartments toward the most transcriptionally active state (A3), and the upregulation of oncogenic genes involved in EMT and proliferation. In contrast, TGF{beta} treatment promotes chromatin compaction, increases the proportion of B compartments, and drives a stepwise reduction in active A subcompartments. Our results highlight the differential roles of HP1 and TGF{beta} in shaping the 3D genome and underscore how precise, stepwise architectural changes contribute to malignant transformation. This study provides critical insight into how chromatin architecture acts as a regulatory layer in breast cancer development. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=138 SRC="FIGDIR/small/705282v1_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@11c7475org.highwire.dtl.DTLVardef@121b305org.highwire.dtl.DTLVardef@1704b64org.highwire.dtl.DTLVardef@1659c34_HPS_FORMAT_FIGEXP M_FIG GRAPHICAL ABSTRACT C_FIG

genomics↗

bioRxiv2023

The BOD1L subunit of the mammalian SETD1A complex sustains the expression of DNA damage repair genes despite restraining H3K4 trimethylation

SETD1A is the histone 3 lysine 4 (H3K4) methyltransferase central to the mammalian version of the highly conserved eight subunit Set1 complex (Set1C) that apparently conveys H3K4 trimethylation (H3K4me3) onto all active Pol II promoters. Accordingly, the Setd1a mouse knock-out dies in early embryogenesis at the epiblast stage and mouse embryonic stem cells (ESCs) die when SETD1A is removed. We report that ESC death is accompanied by loss of expression of DNA repair genes and accumulating DNA damage. BOD1L and BOD1 are homologs of the yeast Set1C subunit, Shg1, and subunits of the mammalian SETD1A and B complexes. We show that the Shg1 homology region binds to a highly conserved central alpha-helix in SETD1A and B. Like mutagenesis of Shg1 in yeast, conditional mutagenesis of Bod1l in ESCs promoted increased H3K4 di- and tri-methylation but also, like loss of SETD1A, loss of expression of DNA repair genes, increased DNA damage and cell death. In contrast to similar losses of DNA repair gene expression, the converse changes in H3K4 methylation after loss of SETD1A or BOD1L implies that H3K4 methylation is not essential for expression of the target DNA repair genes. Because BOD1L becomes highly phosphorylated after DNA damage and acts to protect damaged replication forks, the SETD1A complex, and BOD1L in particular, are key nodes for the DNA damage repair network.

cell biology↗

bioRxiv2021

Binding specificity of ASHH2 CW-domain towards H3K4me1 ligand is coupled to its structural stability through its α1-helix

The CW-domain binds to histone-tail modifications found in different protein families involved in epigenetic regulation and chromatin remodelling. CW-domains recognize the methylation state of the fourth lysine on histone 3, and could therefore be viewed as a reader of epigentic information. The specificity towards different methylation states such as me1, me2 or me3 depends on the particular CW subtype. For example, the CW domain of ASHH2-methyltransferase binds preferentially to H3K4me1, MORC3 binds to both H3K4me2 and me3 modifications, while ZCWPW1 is more specific to H3K4me3. The structural basis for these preferential bindings are not well understood, and recent research suggests that a more complete picture will emerge if dynamical and energetic assessments are included in the analysis of interactions. This study uses fold assessment by NMR in combination with mutagenesis, ITC affinity measurements and thermal denaturation studies to investigate possible couplings between ASHH2 CW selectivity towards H3K4me1 and the stabilization of the domain and loops implicated in binding. Key elements of the binding site - the two tryptophans and the 1-helix form and maintain the binding pocket were perturbed by mutagenesis and investigated. Results show that 1-helix maintains the overall stability of the fold via the I915 and L919 residues, and that correct binding consolidates the loops designated {eta}1, {eta}3, as well as the C-terminal. This consolidation is incomplete for H3K4me3 binding to CW, which experiences a decrease in overall thermal stability upon binding. Moreover, loop-mutations not directly involved in the binding site nonetheless affect the equillibrium positions of key residues.

biophysics↗

bioRxiv2018

The GBAF chromatin remodeling complex binds H3K27ac and mediates enhancer transcription

H3K27ac is associated with regulatory active enhancers, but its exact role in enhancer function remains elusive. Using mass spectrometry-based interaction proteomics, we identified the Super Elongation Complex (SEC) and GBAF, a non-canonical GLTSCR1L- and BRD9-containing SWI/SNF chromatin remodeling complex, to be major interactors of H3K27ac. We systematically characterized the composition of GBAF and the conserved GLTSCR1/1L GiBAF-domain, which we found to be responsible for GBAF complex formation and GLTSCR1L nuclear localization. Inhibition of the bromodomain of BRD9 revealed interaction between GLTSCR1L and H3K27ac to be BRD9-dependent and led to GLTSCR1L dislocation from its preferred binding sites at H3K27ac-associated enhancers. GLTSCR1L disassociation from chromatin resulted in genome-wide downregulation of enhancer transcription while leaving most mRNA expression levels unchanged, except for reduced mRNA levels from loci topologically linked to affected enhancers. Our results indicate that GBAF is an enhancer-associated chromatin remodeler important for transcriptional and regulatory activity of enhancers.\n\nGraphical abstract\n\nO_FIG O_LINKSMALLFIG WIDTH=142 HEIGHT=200 SRC=\"FIGDIR/small/445148_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (32K):\norg.highwire.dtl.DTLVardef@10c54dborg.highwire.dtl.DTLVardef@9730dforg.highwire.dtl.DTLVardef@9985eorg.highwire.dtl.DTLVardef@1f26844_HPS_FORMAT_FIGEXP M_FIG C_FIG

genomics↗