UV-Induced Association of the CSB Remodeling Protein with Chromatin Requires ATP-Dependent Relief of N-Terminal Autorepression

Epigenetics and Progenitor Cells Keystone Program, Fox Chase Cancer Center, Philadelphia, PA 19111, USA.
Molecular cell (Impact Factor: 14.02). 01/2010; 37(2):235-46. DOI: 10.1016/j.molcel.2009.10.027
Source: PubMed


The ATP-dependent chromatin remodeler CSB is essential for transcription-coupled DNA repair, and mutations in CSB lead to Cockayne syndrome. Here, we examined the recruitment of CSB to chromatin after ultraviolet (UV) irradiation and uncovered a regulatory mechanism that ensures the specific association of this remodeler with chromatin. We demonstrate that ATP hydrolysis by CSB is essential for stable CSB-chromatin association after UV irradiation and that defects in this association underlie some forms of Cockayne syndrome. We also show that the N-terminal region of CSB negatively regulates chromatin association during normal cell growth. Of interest, in the absence of the negative regulatory region, ATP hydrolysis becomes dispensable for chromatin association, indicating that CSB uses energy from ATP hydrolysis to overcome the inhibitory effect imposed by its N-terminal region. Together, our results suggest that the recruitment of CSB to lesion-stalled transcription is an ATP-dependent process and involves a gross conformational change of CSB.

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Available from: Yu Zhao
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    • "Current models describe the recruitment of the SNF2/SWI2 ATPase CSB upon stalling of elongating RNA polymerase II (RNAPIIo) to the site of damage, their transient interaction being stabilized in an ATP-dependent manner [15] [22] [23]. This step is followed by the CSB-dependent recruitment of CSA, which functions as a DCAF in the E3 ubiquitin ligase complex consisting of Cullin 4A, DDB1 and Rbx1/ROC1; this complex has common architectural features with the CRL4 DDB2 complex responsible for damage recognition in GG-NER [14]. "
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    ABSTRACT: Nucleotide excision repair (NER) is a key component of the DNA damage response (DDR) and it is essential to safeguard genome integrity against genotoxic insults. The regulation of NER is primarily mediated by protein post-translational modifications (PTMs). The NER machinery removes a wide spectrum of DNA helix distorting lesions, including those induced by solar radiation, through two sub-pathways: global genome nucleotide excision repair (GG-NER) and transcription coupled nucleotide excision repair (TC-NER). Severe clinical consequences associated with inherited NER defects, including premature ageing, neurodegeneration and extreme cancer-susceptibility, underscore the biological relevance of NER. In the last two decades most of the core NER machinery has been elaborately described, shifting attention to molecular mechanisms that either facilitate NER in the context of chromatin or promote the timely and accurate interplay between NER factors and various post-translational modifications. In this review, we summarize and discuss the latest findings in NER. In particular, we focus on emerging factors and novel molecular mechanisms by which NER is regulated.
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    • "In addition, efficient restart of transcription after TC-NER was found to depend on histone methyltransferase DOT1L (17) and on accelerated histone H2A exchange and new histone H3.3 deposition, mediated by the FACT and HIRA histone chaperones, respectively (18,19). Furthermore, the TC-NER key factor CSB exhibits ATP-dependent chromatin remodeling activity in vitro (20,21), which is stimulated by the histone chaperones NAP1L1 and NAP1L4 (22). Although in Caenorhabditis elegans (23) as well as in yeast (24) ATP-dependent chromatin remodeling was suggested to promote TC-NER, it is still unknown whether and how ATP-dependent chromatin remodeling plays a role in mammalian TC-NER. "
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    ABSTRACT: Chromatin compaction of deoxyribonucleic acid (DNA) presents a major challenge to the detection and removal of DNA damage. Helix-distorting DNA lesions that block transcription are specifically repaired by transcription-coupled nucleotide excision repair, which is initiated by binding of the CSB protein to lesion-stalled RNA polymerase II. Using live cell imaging, we identify a novel function for two distinct mammalian ISWI adenosine triphosphate (ATP)-dependent chromatin remodeling complexes in resolving lesion-stalled transcription. Human ISWI isoform SMARCA5/SNF2H and its binding partners ACF1 and WSTF are rapidly recruited to UV-C induced DNA damage to specifically facilitate CSB binding and to promote transcription recovery. SMARCA5 targeting to UV-C damage depends on transcription and histone modifications and requires functional SWI2/SNF2-ATPase and SLIDE domains. After initial recruitment to UV damage, SMARCA5 re-localizes away from the center of DNA damage, requiring its HAND domain. Our studies support a model in which SMARCA5 targeting to DNA damage-stalled transcription sites is controlled by an ATP-hydrolysis-dependent scanning and proofreading mechanism, highlighting how SWI2/SNF2 chromatin remodelers identify and bind nucleosomes containing damaged DNA.
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    • "Additionally, access to DNA is likely to be actively induced by multiple ATP-dependent chromatin-remodeling complexes, which have been implicated in the response of cells to UV irradiation (Table 1). One of the major TC-NER proteins, CSB/ERCC6, contains a SWI2/SNF2 ATPase domain, which is essential for recruitment of the protein to chromatin and to its function in repair [42-45]. CSB is able to remodel chromatin in vitro in an ATP-dependent fashion [46], and is required for the recruitment of NER factors to sites of TC-NER [47], but its precise activity and whether it remodels nucleosomes during TC-NER in vivo remains unknown. "
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