Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Structural basis of telomeric nucleosome recognition by shelterin factor TRF1.

ABSTRACT: Shelterin and nucleosomes are the key players that organize mammalian chromosome ends into the protective telomere caps. However, how they interact with each other at telomeres remains unknown. We report cryo-electron microscopy structures of a human telomeric nucleosome both unbound and bound to the shelterin factor TRF1. Our structures reveal that TRF1 binds unwrapped nucleosomal DNA ends by engaging both the nucleosomal DNA and the histone octamer. Unexpectedly, TRF1 binding shifts the register of the nucleosomal DNA by 1 bp. We discovered that phosphorylation of the TRF1 C terminus and a noncanomical DNA binding surface on TRF1 are critical for its association with telomeric nucleosomes. These insights into shelterin-chromatin interactions have crucial implications for understanding telomeric chromatin organization and other roles of shelterin at telomeres including replication and transcription.

SUBMITTER: Hu H

PROVIDER: S-EPMC10456876 | biostudies-literature | 2023 Aug

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Structural basis of telomeric nucleosome recognition by shelterin factor TRF1.

Hu Hongmiao H van Roon Anne-Marie M AM Ghanim George E GE Ahsan Bilal B Oluwole Abraham O AO Peak-Chew Sew-Yeu SY Robinson Carol V CV Nguyen Thi Hoang Duong THD

Science advances 20230825 34

Shelterin and nucleosomes are the key players that organize mammalian chromosome ends into the protective telomere caps. However, how they interact with each other at telomeres remains unknown. We report cryo-electron microscopy structures of a human telomeric nucleosome both unbound and bound to the shelterin factor TRF1. Our structures reveal that TRF1 binds unwrapped nucleosomal DNA ends by engaging both the nucleosomal DNA and the histone octamer. Unexpectedly, TRF1 binding shifts the regist ...[more]

PMID: 37624885

Similar Datasets

Structural basis of paralog-specific KDM2A/B nucleosome recognition.

Project description:The nucleosome acidic patch is a major interaction hub for chromatin, providing a platform for enzymes to dock and orient for nucleosome-targeted activities. To define the molecular basis of acidic patch recognition proteome wide, we performed an amino acid resolution acidic patch interactome screen. We discovered that the histone H3 lysine 36 (H3K36) demethylase KDM2A, but not its closely related paralog, KDM2B, requires the acidic patch for nucleosome binding. Despite fundamental roles in transcriptional repression in health and disease, the molecular mechanisms governing nucleosome substrate specificity of KDM2A/B, or any related JumonjiC (JmjC) domain lysine demethylase, remain unclear. We used a covalent conjugate between H3K36 and a demethylase inhibitor to solve cryogenic electron microscopy structures of KDM2A and KDM2B trapped in action on a nucleosome substrate. Our structures show that KDM2-nucleosome binding is paralog specific and facilitated by dynamic nucleosomal DNA unwrapping and histone charge shielding that mobilize the H3K36 sequence for demethylation.

| S-EPMC10159993 | biostudies-literature

Structural Basis for Shelterin Bridge Assembly.

Project description:Telomere elongation through telomerase enables chromosome survival during cellular proliferation. The conserved multifunctional shelterin complex associates with telomeres to coordinate multiple telomere activities, including telomere elongation by telomerase. Similar to the human shelterin, fission yeast shelterin is composed of telomeric sequence-specific double- and single-stranded DNA-binding proteins, Taz1 and Pot1, respectively, bridged by Rap1, Poz1, and Tpz1. Here, we report the crystal structure of the fission yeast Tpz1475-508-Poz1-Rap1467-496 complex that provides the structural basis for shelterin bridge assembly. Biochemical analyses reveal that shelterin bridge assembly is a hierarchical process in which Tpz1 binding to Poz1 elicits structural changes in Poz1, allosterically promoting Rap1 binding to Poz1. Perturbation of the cooperative Tpz1-Poz1-Rap1 assembly through mutation of the "conformational trigger" in Poz1 leads to unregulated telomere lengthening. Furthermore, we find that the human shelterin counterparts TPP1-TIN2-TRF2 also assemble hierarchically, indicating cooperativity as a conserved driving force for shelterin assembly.

| S-EPMC5698806 | biostudies-literature

Structural basis for COMPASS recognition of an H2B-ubiquitinated nucleosome.

Project description:Methylation of histone H3K4 is a hallmark of actively transcribed genes that depends on mono-ubiquitination of histone H2B (H2B-Ub). H3K4 methylation in yeast is catalyzed by Set1, the methyltransferase subunit of COMPASS. We report here the cryo-EM structure of a six-protein core COMPASS subcomplex, which can methylate H3K4 and be stimulated by H2B-Ub, bound to a ubiquitinated nucleosome. Our structure shows that COMPASS spans the face of the nucleosome, recognizing ubiquitin on one face of the nucleosome and methylating H3 on the opposing face. As compared to the structure of the isolated core complex, Set1 undergoes multiple structural rearrangements to cement interactions with the nucleosome and with ubiquitin. The critical Set1 RxxxRR motif adopts a helix that mediates bridging contacts between the nucleosome, ubiquitin and COMPASS. The structure provides a framework for understanding mechanisms of trans-histone cross-talk and the dynamic role of H2B ubiquitination in stimulating histone methylation.

| S-EPMC7039682 | biostudies-literature

Structural Basis for Recognition of Ubiquitylated Nucleosome by Dot1L Methyltransferase.

Project description:Histone H3 lysine 79 (H3K79) methylation is enriched on actively transcribed genes, and its misregulation is a hallmark of leukemia. Methylation of H3K79, which resides on the structured disk face of the nucleosome, is mediated by the Dot1L methyltransferase. Dot1L activity is part of a trans-histone crosstalk pathway, requiring prior histone H2B ubiquitylation of lysine 120 (H2BK120ub) for optimal activity. However, the molecular details describing both how Dot1L binds to the nucleosome and why Dot1L is activated by H2BK120 ubiquitylation are unknown. Here, we present the cryoelectron microscopy (cryo-EM) structure of Dot1L bound to a nucleosome reconstituted with site-specifically ubiquitylated H2BK120. The structure reveals that Dot1L engages the nucleosome acidic patch using a variant arginine anchor and occupies a conformation poised for methylation. In this conformation, Dot1L and ubiquitin interact directly through complementary hydrophobic surfaces. This study establishes a path to better understand Dot1L function in normal and leukemia cells.

| S-EPMC6392056 | biostudies-literature

Structural basis of nucleosome recognition by the conserved Dsup and HMGN nucleosome-binding motif.

Project description:The tardigrade damage suppressor (Dsup) and vertebrate high mobility group N (HMGN) proteins bind specifically to nucleosomes via a conserved motif whose structure has not been experimentally determined. Here we used cryo-EM to show that both proteins bind to the nucleosome acidic patch via analogous arginine anchors with one molecule bound to each face of the nucleosome. We additionally employed the natural promoter-containing 5S rDNA sequence for structural analysis of the nucleosome. These structures of an ancient nucleosome-binding motif suggest that there is an untapped realm of proteins with a related mode of binding to chromatin.

| S-EPMC11741339 | biostudies-literature

Structural basis of paralog-specific KDM2A/B nucleosome recognition

Project description:The nucleosome acidic patch is a major interaction hub for chromatin, providing a platform for enzymes to dock and orient for nucleosome-targeted activities. In order to define the molecular basis of acidic patch recognition proteome-wide, we performed an amino acid resolution acidic patch interactome screen. We discovered that the histone H3 lysine 36 (H3K36) demethylase KDM2A, but not its closely related paralog, KDM2B, requires the acidic patch for nucleosome binding. These KDM2 family JumonjiC (JmjC) domain lysine demethylases are critical to heterochromatin formation and are commonly misregulated in cancer. Despite fundamental roles in transcriptional regulation in health and disease, the molecular mechanisms governing nucleosome substrate specificity of KDM2A/B, or any other JmjC lysine demethylases, remain unclear. We used a covalent JmjC inhibitor to solve cryo-EM structures of KDM2A and KDM2B trapped in action on the nucleosome. Our structures show that KDM2-nucleosome binding is paralog-specific and facilitated by dynamic nucleosomal DNA unwrapping and histone charge shielding that mobilize the H3K36 sequence for demethylation.

2023-02-14 | PXD032791 | Pride

Structural basis of G-quadruplex DNA recognition by the yeast telomeric protein Rap1.

Project description:G-quadruplexes are four-stranded nucleic acid structures involved in multiple cellular pathways including DNA replication and telomere maintenance. Such structures are formed by G-rich DNA sequences typified by telomeric DNA repeats. Whilst there is evidence for proteins that bind and regulate G-quadruplex formation, the molecular basis for this remains poorly understood. The budding yeast telomeric protein Rap1, originally identified as a transcriptional regulator functioning by recognizing double-stranded DNA binding sites, was one of the first proteins to be discovered to also bind and promote G-quadruplex formation in vitro. Here, we present the 2.4 Å resolution crystal structure of the Rap1 DNA-binding domain in complex with a G-quadruplex. Our structure not only provides a detailed insight into the structural basis for G-quadruplex recognition by a protein, but also gives a mechanistic understanding of how the same DNA-binding domain adapts to specifically recognize different DNA structures. The key observation is the DNA-recognition helix functions in a bimodal manner: In double-stranded DNA recognition one helix face makes electrostatic interactions with the major groove of DNA, whereas in G-quadruplex recognition a different helix face is used to make primarily hydrophobic interactions with the planar face of a G-tetrad.

| S-EPMC7192608 | biostudies-literature

Structural basis of selective ubiquitination of TRF1 by SCFFbx4.

Project description:TRF1 is a critical regulator of telomere length. As such, TRF1 levels are regulated by ubiquitin-dependent proteolysis via an SCF E3 ligase where Fbx4 contributes to substrate specification. Here, we report the crystal structure of the Fbx4-TRF1 complex at 2.4 A resolution. Fbx4 contains an unusual substrate-binding domain that adopts a small GTPase fold. Strikingly, this atypical GTPase domain of Fbx4 binds to a globular domain of TRF1 through an intermolecular beta sheet, instead of recognizing short peptides/degrons as often seen in other F-box protein-substrate complexes. Importantly, mutations in this interface abrogate Fbx4-dependent TRF1 binding and ubiquitination. Furthermore, the data demonstrate that recognition of TRF1 by SCF(Fbx4) is regulated by another telomere protein, TIN2. Our results reveal an atypical small GTPase domain within Fbx4 as a substrate-binding motif for SCF(Fbx4) and uncover a mechanism for selective ubiquitination and degradation of TRF1 in telomere homeostasis control.

| S-EPMC6097615 | biostudies-literature

Shelterin reduces the accessibility of telomeric overhangs.

Project description:Telomeres terminate with a 50-300 bases long single-stranded G-rich overhang, which can be misrecognized as a DNA damage repair site. Shelterin plays critical roles in maintaining and protecting telomere ends by regulating access of various physiological agents to telomeric DNA, but the underlying mechanism is not well understood. Here, we measure how shelterin affects the accessibility of long telomeric overhangs by monitoring transient binding events of a short complementary peptide nucleic acid (PNA) probe using FRET-PAINT in vitro. We observed that the POT1 subunit of shelterin reduces the accessibility of the PNA probe by ∼2.5-fold, indicating that POT1 effectively binds to and protects otherwise exposed telomeric sequences. In comparison, a four-component shelterin stabilizes POT1 binding to the overhang by tethering POT1 to the double-stranded telomeric DNA and reduces the accessibility of telomeric overhangs by ∼5-fold. This enhanced protection suggests shelterin restructures the junction between single and double-stranded telomere, which is otherwise the most accessible part of the telomeric overhang.

| S-EPMC9825182 | biostudies-literature