A DNA Damage Response Screen Identifies RHINO, a 9-1-1 and TopBP1 Interacting Protein Required for ATR Signaling

Abstract

The DNA damage response (DDR) is a protein kinase cascade that orchestrates DNA repair processes via transcriptional and post-translational mechanisms. Cell cycle arrest is a hallmark of the DDR. We performed a damage-induced cell cycle arrest screen and uncovered a critical role for Fanconi anemia (FA) and homologous recombination (HR) proteins in ATR signaling. HR was required to maintain prolonged cell cycle arrest and to prevent massive genomic instability. Over 100 high scoring DDR candidates were interrogated for their roles in the DDR. Three proteins, INTS7, CLOCK and a novel protein RHINO, are recruited to sites of DNA damage. RHINO independently binds the Rad9-Rad1-Hus1 complex (9-1-1) and TopBP1. RHINO is recruited to sites of DNA damage by the 9-1-1 complex and is necessary to promote Chk1 activation. We suggest that RHINO functions together with the 9-1-1 complex and TopBP1 to fully activate ATR.

Core circadian protein CLOCK is a positive regulator of NF-κB–mediated transcription

“…This result also is consistent with our transcriptional assay showing functional cooperation of CLOCK and CBP in activating the κB-Luc reporter and with previously published data demonstrating the interaction of both CLOCK and its homolog NPAS2 with chromatin-modifying enzymes on E-box-containing promoters (29,30). It is noteworthy that recently CLOCK was identified as one of only three proteins that are recruited to sites of dsDNA breaks (31). Although the detailed mechanism and functional significance of this finding have not been investigated, it represents another example of the BMAL1-independent function of CLOCK and suggests that CLOCK may be involved in DNA repair by recruiting chromatin-modifying or DNA repair enzymes to the sites of DNA lesions by a mechanism similar to NF-κB coactivation.…”

Phosphorylation of the Cryptochrome 1 C-terminal Tail Regulates Circadian Period Length

“…Furthermore, loss of various clock components, including CLOCK, BMAL1, PER1, and PER2, have been linked to increased chronic sensitivity to DNA cross-linking reagents, increased tumor development, and deficiencies in DNA damage responses (63)(64)(65). In addition, the CLOCK protein is recruited to sites of DNA damage (66), and DNA damage can act as a resetting cue for the mammalian circadian clock (67). Therefore, a role for DNA-PK in the regulation of CRY1 stability and period control is another example of the relationships between these pathways.…”

TopBP1-mediated DNA processing during mitosis

“…35 Also, the protein RHINO that binds both the 9-1-1 and TopBP1 is required for full activation of ATR. 36,37 Somewhat contradictory, TopBP1 has been shown to localize to stalled replication forks independently of the 9-1-1 complex, and rather be responsible for recruitment of 9-1-1. 38,39 In line with this, recruitment of TopBP1 to ATR activating DNA structures in Xenopus extracts was shown to rely on the MRN complex.…”