CUX1 transcription factor is required for optimal ATM/ATR-mediated responses to DNA damage

Abstract

The p110 Cut homeobox 1 (CUX1) transcription factor regulates genes involved in DNA replication and chromosome segregation. Using a genome-wide-approach, we now demonstrate that CUX1 also modulates the constitutive expression of DNA damage response genes, including ones encoding ATM and ATR, as well as proteins involved in DNA damage-induced activation of, and signaling through, these kinases. Consistently, RNAi knockdown or genetic inactivation of CUX1 reduced ATM/ATR expression and negatively impacted hallmark protective responses mediated by ATM and ATR following exposure to ionizing radiation (IR) and UV, respectively. Specifically, abrogation of CUX1 strongly reduced ATM autophosphorylation after IR, in turn causing substantial decreases in (i) levels of phospho-Chk2 and p53, (ii) γ-H2AX and Rad51 DNA damage foci and (iii) the efficiency of DNA strand break repair. Similarly remarkable reductions in ATR-dependent responses, including phosphorylation of Chk1 and H2AX, were observed post-UV. Finally, multiple cell cycle checkpoints and clonogenic survival were compromised in CUX1 knockdown cells. Our results indicate that CUX1 regulates a transcriptional program that is necessary to mount an efficient response to mutagenic insult. Thus, CUX1 ensures not only the proper duplication and segregation of the genetic material, but also the preservation of its integrity.

CUX1, a haploinsufficient tumour suppressor gene overexpressed in advanced cancers

“…Using transcription and cellbased assays, a role for p110 CUX1 was shown in many cellular processes, notably in cell cycle progression and cell proliferation 21,22 , strengthening of the spindle assembly checkpoint 19 , establishment of a transcriptional programme that enables efficient DNA damage responses 23 , and cell migration and invasion 13,42 . In addition, from RNA interference (RNAi)-mediated knockdown and genetic inactivation, CUX1 was shown to be required for the resistance to apoptotic signals in pancreatic cancer cells 14 , the repression cytokine genes associated with M1 macrophages 43 , and dendrite branching and spine development in cortical neurons 34 .…”

“…Indeed, Cux1 −/− MEFs exhibit increased genomic instability 23 . Moreover, Cux1 +/− heterozygous MEFs are haploinsufficient for DNA repair 18 .…”

“…Non-oncogene addictions involving CUX1 As p110 CUX1 activates distinct sets of genes involved in DNA replication 41 , the DNA damage response 23 and the spindle assembly checkpoint 19 , we understand that its roles in the cell cycle are to prepare cells for DNA replication, promote maintenance of genome integrity and ensure proper chromosomal segregation at the end of the cell cycle. In addition, p200 CUX1 promotes genome stability through its role in base excision repair 18 .…”

“…Cell-based assays have shown transcriptional roles for CUX1 in cell cycle progression 21,22 , DNA damage responses 23 , and resistance to apoptotic signals 14 and other pathways (FIG. 2).…”

Inhibition of cathepsin L sensitizes human glioma cells to ionizing radiation in vitro through NF-κB signaling pathway

“…CUX1 plays an important role in the transcriptional regulation of chemotactic factors that are mediated by NF-κB [35] . Furthermore, CUX1 regulates ATM expression in response to DNA damage by binding to the promoter of the DDR gene ATM; this demonstrates that CUX1 is required for ATM-/ATRmediated cellular responses to genotoxic stress following IR exposure [36] . Cathepsin L most likely regulates the activity of NF-κB and its downstream effectors via the CUX1 pathway.…”