Subunit Rtt102 Controls the Conformation of the Arp7/9 Heterodimer and Its Interactions with Nucleotide and the Catalytic Subunit of SWI/SNF Remodelers
Year: 2013
Type: article
Abstract: Background: The function of subunit Rtt102 of SWI/SNF remodelers is largely unknown.Results: Rtt102 induces a conformational change in the Arp7/9 heterodimer, promoting nucleotide binding and restricting binding of Arp7/9 to a shorter segment of the HSA domain.Conclusion: Rtt102 stabilizes the structure of Arp7/9-containing remodelers.Significance: This work establishes Rtt102 as a modulator of SWI/SNF remodeler structure through effects on the Arp7/9 heterodimer. Chromatin-remodeling complexes are assembled around a catalytic subunit that contains a central ATPase domain and flanking sequences that recruit auxiliary subunits. The catalytic subunits of SWI/SNF remodelers recruit Arp7/9 through a helicase/SANT-associated (HSA) domain N-terminal to the ATPase domain. Arp7/9-containing remodelers also carry the auxiliary subunit Rtt102, but the role of this subunit is poorly understood.Here, we show that Rtt102 binds with nanomolar affinity to the Arp7/9 heterodimer and modulates its conformation and interactions with the ATPase subunit and nucleotide.When bound to Rtt102, Arp7/9 interacts with a shorter segment of the HSA domain.Structural analysis by small-angle x-ray scattering further shows that when bound to Rtt102, the complex of Arp7/9 with the catalytic subunit assumes a more stable compact conformation.We also found that Arp7, Arp9, and Arp7/9 interact very weakly with ATP, but Rtt102 promotes high-affinity ATP binding to a single site in the heterodimer.Collectively, the results establish a function for subunit Rtt102 as a stabilizing factor for the Arp7/9 heterodimer, enhancing its interaction with nucleotide and controlling the conformation of SWI/SNF remodelers in an Arp7/9-dependent manner.In eukaryotic cells, DNA is wrapped around histone octamers (consisting of two copies of core histones H2A, H2B, H3, and H4) to form the nucleosome, which constitutes the basic building block of chromatin (1).Cells use chromatin-remodeling complexes (remodelers) to reversibly alter chromatin structure and allow regulatory proteins to interact with the DNA during processes such as transcription, DNA replication, and repair (2).Remodeler dysfunction can lead to a wide range of diseases, including cancer, cardiomyopathies, neurodevelop-mental disorders, and deafness (2-6).Remodelers are large protein complexes that belong to four different families (2).They vary in their subunit composition, but all contain a catalytic subunit featuring a conserved helicase SF2 (superfamily 2) ATPase domain (7).The catalytic core of the ATPase consists of two recA domains (2, 8, 9) that cooperate to propel ATP-dependent changes in chromatin structure, including histone octamer sliding, DNA looping, and histone substitution (2, 10, 11).N-and C-terminal to the recA domains, the sequences of the catalytic subunits of the four families of remodelers diverge.These divergent regions frequently serve as a platform for recruitment of other remodeler subunits, generally known as auxiliary subunits.Auxiliary subunits serve diverse functions, including histone recognition and modulation of the ATPase activity of the catalytic subunit (2).Two families of remodelers, SWI/SNF and INO80, contain among their auxiliary subunits actin and actin-related proteins (Arps) 3 (2, 12-14).In the cytoplasm, actin and Arps are part of the actin cytoskeleton that plays crucial roles in cell motility, endocytosis, and the maintenance of cell morphology (15).In the nucleus, actin and Arps form part of large macromolecular complexes that are generally involved in the regulation of gene expression (16,17).The specific role of actin and Arps within remodelers is not fully understood, yet emerging evidence suggests that they may regulate the ATPase activity of remodelers (12, 18 -20) and may also play a role in nucleosome targeting (21)(22)(23).Actin and Arps are recruited to remodelers through interaction with an ϳ80-amino acid (aa) region N-terminal to the recA domains, known as the helicase/SANT-associated (HSA) domain ( 19).The HSA domain of the two INO80 family remodelers (INO80 and SWR1) recruits actin and Arp4, as well as Arp8 in the case of INO80 (12,19,24).In SWI/SNF family remodelers (RSC and SWI/SNF), the HSA domain binds Arp7
Source: Journal of Biological Chemistry
Institution: University of Pennsylvania
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $3,430
OpenAlex ID: W1978364504