OB-F and the wh-domain are two protein interaction domains. A, B, C, and D are DNA binding domains (DBDs). The formation of specific configurations and associated functions are thought to be regulated by post-translational modifications of RPA including phosphorylation, acetylation, sumoylation, and ubiquitination 4, 36.Ī Three RPA subunits RPA70, RPA32, and RPA14 form a heterotrimer and harbor multiple oligosaccharide/oligonucleotide (OB) domains. The flexible linkers allow the domains of RPA to form various configurations (defined as the relative positions of the DBDs and PIDs) and the prevailing hypothesis is that one or more of these configurations drive specific DNA metabolic roles 4, 8, 10, 11, 30, 31, 32, 33, 34, 35. An N-terminal ~40 aa region in RPA32 is extensively phosphorylated by a slew of kinases (Fig. The other PID is a winged helix (wh) domain located at the C-terminus of RPA32 (PID 32C) and connected to DBD-D by a 34 aa disordered linker. There are two PIDs one is OB-F situated at the N-terminus of RPA70 (PID 70N) and connected to DBD-A through a disordered 80 aa linker. The heterotrimer is held together through extensive physical interactions between DBD-C, DBD-D and the RPA14 subunit (trimerization core Fig. DBDs-A, B, and C are situated in the large RPA70 subunit and are connected by flexible linkers. Four OB-folds (DBDs-A, B, C, and D) contribute most to ssDNA interactions. There are six oligonucleotide/oligosaccharide binding (OB) folds labeled A-F (Fig. To coordinate such diverse functions, RPA utilizes a unique structural assembly of DNA binding domains (DBDs) and protein interaction domains (PIDs) situated across three subunits - RPA70, RPA32, and RPA14 17, 18, 19. In concert with RAD52, RPA facilitates mitotic DNA synthesis (MiDAS) to counteract DNA replication stress at common fragile sites loci on the chromosomes 15, 16. For example, RPA activates a mitosis-specific R-loop driven ATR pathway for faithful segregation of chromosomes 14. In addition, several new cell cycle-specific functions have also been recently uncovered. RPA also hands-off the DNA to these enzymes and correctly positions them on appropriate chromosomal structures to facilitate their catalytic activity 11, 12, 13. RPA physically interacts with over three dozen DNA processing enzymes and recruits them to the site of DNA metabolism 4, 8, 9, 10. RPA-ssDNA complexes are important for the activation of ATR signaling response and for a mode of double-strand break repair triggered by ATM 5, 6, 7. It binds to ssDNA with high affinity ( K D < 10 −10 M) and protects it from degradation by exo- and endonucleases 3. RPA performs several essential functions in the cell. RPA also serves as a protein-interaction hub to recruit other proteins onto DNA and coordinates almost all DNA metabolic processes including replication, repair, recombination, and telomere maintenance 4, 5, 6. Protection of transiently exposed ssDNA throughout the cell cycle is achieved through binding of Replication Protein A (RPA) 3. Maintaining genomic integrity during chromosome replication, condensation, and segregation relies on regulatory mechanisms that are distinct to each phase of the cell cycle 1, 2. We showcase a critical Aurora B-RPA signaling axis in mitosis that is essential for maintaining genomic integrity. Furthermore, phosphorylation impairs RPA binding to DSS1 that likely suppresses homologous recombination during mitosis by preventing recruitment of DSS1-BRCA2 to exposed ssDNA. Phosphorylation at Ser-384 remodels the protein interaction domains of RPA. Disruption of Ser-384 phosphorylation in RPA70 leads to defects in chromosome segregation with loss of viability and a feedback modulation of Aurora B activity. Aurora B phosphorylates Ser-384 in the DNA binding domain B of the large RPA70 subunit and highlights a mode of regulation distinct from RPA32. Here, we have uncovered a mitosis-specific regulation of RPA by Aurora B kinase. RPA is a heterotrimer composed of RPA70, RPA32 and RPA14 subunits and is predominantly regulated through hyperphosphorylation of RPA32 in response to DNA damage. However, the mechanisms that regulate RPA specifically during unperturbed mitotic progression are poorly resolved. Resolution of replication and recombination intermediates and protection of vulnerable single-stranded DNA (ssDNA) intermediates during mitotic progression requires the ssDNA binding protein Replication Protein A (RPA). Errors in chromosome segregation underlie genomic instability associated with cancers.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |