Structural highlights
Function
RAD9A_HUMAN Component of the 9-1-1 cell-cycle checkpoint response complex that plays a major role in DNA repair. The 9-1-1 complex is recruited to DNA lesion upon damage by the RAD17-replication factor C (RFC) clamp loader complex. Acts then as a sliding clamp platform on DNA for several proteins involved in long-patch base excision repair (LP-BER). The 9-1-1 complex stimulates DNA polymerase beta (POLB) activity by increasing its affinity for the 3'-OH end of the primer-template and stabilizes POLB to those sites where LP-BER proceeds; endonuclease FEN1 cleavage activity on substrates with double, nick, or gap flaps of distinct sequences and lengths; and DNA ligase I (LIG1) on long-patch base excision repair substrates. The 9-1-1 complex is necessary for the recruitment of RHNO1 to sites of double-stranded breaks (DSB) occurring during the S phase. RAD9A possesses 3'->5' double stranded DNA exonuclease activity. Its phosphorylation by PRKCD may be required for the formation of the 9-1-1 complex.[1] [2]
Publication Abstract from PubMed
The RAD9-RAD1-HUS1 complex (9-1-1) is a eukaryotic DNA clamp with a crucial role at checkpoints for DNA damage. The ring-like structure of 9-1-1 is opened for loading onto 5' recessed DNA by the clamp-loader RAD17 RFC-like complex (RAD17-RLC), in which the RAD17 subunit is responsible for specificity to 9-1-1. Loading of 9-1-1 is required for activation of the ATR-CHK1 checkpoint pathway and the activation is stimulated by a 9-1-1 interacting protein, RHINO, which interacts with 9-1-1 via a recently identified RAD1-binding motif. This discovery led to the hypothesis that other interacting proteins may contain a RAD1-binding motif as well. Here, we show that vertebrate RAD17 proteins also have a putative RAD1-binding motif in their N-terminal regions, and we report the crystal structure of human 9-1-1 bound to a human RAD17 peptide incorporating the motif at 2.1 A resolution. Our structure confirms that the N-terminal region of RAD17 binds to the RAD1 subunit of 9-1-1 via specific interactions. Furthermore, we show that the RAD1-binding motif of RHINO disturbs the interaction of the N-terminal region of RAD17 with 9-1-1. Our results provide deeper understanding of how RAD17-RLC specifically recognizes 9-1-1 and imply that RHINO has a functional role in 9-1-1 loading/unloading and checkpoint activation.
The 9-1-1 DNA clamp subunit RAD1 forms specific interactions with clamp loader RAD17, revealing functional implications for binding-protein RHINO.,Hara K, Hishiki A, Hoshino T, Nagata K, Iida N, Sawada Y, Ohashi E, Hashimoto H J Biol Chem. 2023 Feb 23:103061. doi: 10.1016/j.jbc.2023.103061. PMID:36841485[3]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Bessho T, Sancar A. Human DNA damage checkpoint protein hRAD9 is a 3' to 5' exonuclease. J Biol Chem. 2000 Mar 17;275(11):7451-4. PMID:10713044
- ↑ Cotta-Ramusino C, McDonald ER 3rd, Hurov K, Sowa ME, Harper JW, Elledge SJ. A DNA damage response screen identifies RHINO, a 9-1-1 and TopBP1 interacting protein required for ATR signaling. Science. 2011 Jun 10;332(6035):1313-7. doi: 10.1126/science.1203430. PMID:21659603 doi:10.1126/science.1203430
- ↑ Hara K, Hishiki A, Hoshino T, Nagata K, Iida N, Sawada Y, Ohashi E, Hashimoto H. The 9-1-1 DNA clamp subunit RAD1 forms specific interactions with clamp loader RAD17, revealing functional implications for binding-protein RHINO. J Biol Chem. 2023 Feb 24;299(4):103061. PMID:36841485 doi:10.1016/j.jbc.2023.103061
