Related Experiment Video

Updated: Jul 4, 2025

Deciphering Molecular Mechanism of Histone Assembly by DNA Curtain Technique
06:32

Deciphering Molecular Mechanism of Histone Assembly by DNA Curtain Technique

Published on: March 9, 2022

1.8K

Asymmetric nucleosome PARylation at DNA breaks mediates directional nucleosome sliding by ALC1

Luka Bacic1, Guillaume Gaullier1,2, Jugal Mohapatra3

  • 1Department of Cell and Molecular Biology, Science for Life Laboratory, Uppsala University, 75124, Uppsala, Sweden.

Nature Communications
|February 2, 2024
PubMed

Insights

The chromatin remodeler ALC1 is recruited to DNA damage sites by poly(ADP-ribose) and directs nucleosome sliding away from breaks. This mechanism aids DNA repair factor accessibility.

Area of Science:

  • Molecular Biology
  • Biochemistry
  • Structural Biology

Background:

  • The chromatin remodeler ALC1 is activated by poly(ADP-ribose) (PAR) chains generated by PARP1/PARP2 and HPF1 upon DNA damage.
  • ALC1 is a promising cancer drug target, but its precise recruitment mechanism to ADP-ribosylated nucleosomes and subsequent nucleosome positioning near DNA breaks remain unclear.

Purpose of the Study:

  • To elucidate the mechanism of ALC1 recruitment to ADP-ribosylated nucleosomes and its role in nucleosome positioning near DNA breaks.

Main Methods:

  • Generation of nucleosomes with asymmetric ADP-ribosylation on the histone H2B tail.
  • Cryo-electron microscopy (cryo-EM) to determine the structure of ALC1 bound to asymmetric nucleosomes.
  • Single-molecule Förster Resonance Energy Transfer (smFRET) to study nucleosome sliding dynamics.

Main Results:

  • PARP1/HPF1 preferentially initiates ADP-ribosylation on the histone H2B tail proximal to the DNA break.
  • The cryo-EM structure reveals ALC1 preferentially engages with the asymmetrically ADP-ribosylated nucleosome.
  • smFRET experiments demonstrate that asymmetric ALC1 recruitment results in directed nucleosome sliding away from the ADP-ribosylation site.

Conclusions:

  • ALC1 is recruited asymmetrically to ADP-ribosylated nucleosomes, driven by the location of PAR chains on histone H2B.
  • This asymmetric recruitment triggers directed nucleosome sliding, moving nucleosomes away from DNA breaks.
  • The ALC1-mediated nucleosome repositioning facilitates accessibility of DNA breaks to repair machinery, highlighting a key step in DNA damage response.

More Related Videos

Examination of Proteins Bound to Nascent DNA in Mammalian Cells Using BrdU-ChIP-Slot-Western Technique09:14

Examination of Proteins Bound to Nascent DNA in Mammalian Cells Using BrdU-ChIP-Slot-Western Technique

Published on: January 14, 2016

9.2K
Author Spotlight: Efficient Nucleosome Reconstitution for Single-Molecule Techniques05:58

Author Spotlight: Efficient Nucleosome Reconstitution for Single-Molecule Techniques

Published on: September 6, 2024

1.1K

Related Concept Videos

Nucleosome Remodeling02:54

Nucleosome Remodeling

Nucleosomes are the basic units of chromatin compaction. Each nucleosome consists of the DNA bound tightly around a histone core, which makes the DNA inaccessible to DNA binding proteins such as DNA polymerase and RNA polymerase. Hence, the fundamental problem is to ensure access to DNA when appropriate, despite the compact and protective chromatin structure.
Nucleosome remodeling complex
Eukaryotic cells have specialized enzymes called ATP-dependent nucleosome remodeling enzymes. These enzymes...
9.1K
Restarting Stalled Replication Forks02:37

Restarting Stalled Replication Forks

DNA replication is initiated at sites containing predefined DNA sequences known as origins of replication. DNA is unwound at these sites by the minichromosome maintenance (MCM) helicase and other factors such as Cdc45 and the associated GINS complex.The unwound single strands are protected by replication protein A (RPA) until DNA polymerase starts synthesizing DNA at the 5’ end of the strand in the same direction as the replication fork. To prevent the replication fork from falling apart,...
5.8K
Forces Acting on Chromosomes02:11

Forces Acting on Chromosomes

During mitosis, chromosome movements occur through the interplay of multiple piconewton level forces. In prometaphase, these forces help in chromosome assembly or congression at the equatorial plane, eventually leading to their alignment at the metaphase plate. The forces acting on the chromosomes are space and time-dependent; therefore, they vary with the position of the chromosomes as the cell progresses through mitosis. 
Microtubules and motor proteins exert two types of forces on...
3.3K
Homologous Recombination02:31

Homologous Recombination

The basic reaction of homologous recombination (HR) involves two chromatids that contain DNA sequences sharing a significant stretch of identity. One of these sequences uses a strand from another as a template to synthesize DNA in an enzyme-catalyzed reaction. The final product is a novel amalgamation of the two substrates. To ensure an accurate recombination of sequences, HR is restricted to the S and G2 phases of the cell cycle. At these stages, the DNA has been replicated already and the...
50.5K
Attachment of Sister Chromatids02:57

Attachment of Sister Chromatids

As cells progress into mitosis, the nuclear envelope breaks down, and the condensed chromosomes are exposed to the array of bipolar microtubules of the mitotic spindle. The kinetochore, a large, disc-shaped protein complex, is present at the centromere region of the sister chromatids and acts as a binding site for the microtubules.  Usually, the plus-end of a single microtubule is embedded within the kinetochore. However, some kinetochores first establish lateral contact with the side-wall...
3.3K
DNA Damage can Stall the Cell Cycle02:37

DNA Damage can Stall the Cell Cycle

In response to DNA damage, cells can pause the cell cycle to assess and repair the breaks. However, the cell must check the DNA at certain critical stages during the cell cycle. If the cell cycle pauses before DNA replication, the cells will contain twice the amount of DNA. On the other hand, if cells arrest after DNA replication but before mitosis, they will contain four times the normal amount of DNA. With a host of specialized proteins at their disposal,cells must use the right protein at...
9.2K