ATM–Dependent MiR-335 Targets CtIP and Modulates the DNA Damage Response

Abstract

ATM plays a critical role in cellular responses to DNA double-strand breaks (DSBs). We describe a new ATM–mediated DSB–induced DNA damage response pathway involving microRNA (miRNA): irradiation (IR)-induced DSBs activate ATM, which leads to the downregulation of miR-335, a miRNA that targets CtIP, which is an important trigger of DNA end resection in homologous recombination repair (HRR). We demonstrate that CREB is responsible for a large portion of miR-335 expression by binding to the promoter region of miR-335. CREB binding is greatly reduced after IR, corroborating with previous studies that IR-activated ATM phosphorylates CREB to reduce its transcription activity. Overexpression of miR-335 in HeLa cells resulted in reduced CtIP levels and post-IR colony survival and BRCA1 foci formation. Further, in two patient-derived lymphoblastoid cell lines with decreased post-IR colony survival, a “radiosensitive” phenotype, we demonstrated elevated miR-335 expression, reduced CtIP levels, and reduced BRCA1 foci formation. Colony survival, BRCA1 foci, and CtIP levels were partially rescued by miRNA antisense AMO-miR-335 treatment. Taken together, these findings strongly suggest that an ATM–dependent CREB–miR-335–CtIP axis influences the selection of HRR for repair of certain DSB lesions.

DNA damage responsive miR-33b-3p promoted lung cancer cells survival and cisplatin resistance by targeting p21WAF1/CIP1

“…18 Another group showed that irradiation (IR) lead to the downregulation of miR-335 in an ATM dependent manner, and miR-335 was involved in homologous recombination repair (HRR) via suppressing CtIP expression. 24 In addition, miR15b has been established to be up-regulated following exposure to diverse stress-inducing agents, including ionizing radiation, etoposide, and hydrogen peroxide, which significantly influenced the cell cycle progression by targeting WIP1. 25 The demonstration that miR-33b-3p was dramatically downregulated when exposed to cisplatin and impacted on DDR by negative regulation of p21, further enlarged the knowledge and confirmed the effects of miRNAs on DNA damage response.…”

Diverse microRNAs with convergent functions regulate tumorigenesis

“…The loss of checkpoint control is required for cancer initiation and development (43,44). Thus, there is a clear direct connection between miRNAs and cancer formation, which will not be discussed further in the present review.…”

“…It has been previously reported that miR-34 may be induced by p53 and subsequently cause G1 phase cell cycle arrest (3,17), while miR-335 may be downregulated by activated ATM (43). Therefore, it appears that the genes involved in cell cycle checkpoint control are primarily Figure 1.…”

“…In addition to its regulatory function in signaling pathways, miR-335 has roles in at least two pathways involved in cell cycle control, namely ataxia telangiectasia mutated (ATM)-dependent DNA damage control (43) and octamer-binding transcription factor 4-retinoblastoma protein (Oct4-pRB)-dependent stem cell renewal/cell cycle control (44). In the ATM pathway, irradiation-activated ATM downregulates miR-335 via cyclic adenosine monophosphate response element binding protein, which subsequently activates C terminal binding protein interaction protein, which in turn recruits breast cancer 1, early onset to double strand breaks (43). During stem cell renewal, miR-335 is able to regulate the cell cycle by controlling the activities of the Oct4-pRb signaling pathway.…”

“…Previous studies have demonstrated that the expression levels of miR-335 are cancer type-specific. Thus, downregulation of miR-335 is observed in certain types of metastatic breast cancer (45), whereas upregulation is observed in the breast cancer cell line MCF7 (43). Regarding its role in ATM-dependent DNA damage control, Martin et al (43) suggested that differential expression levels of miR-335 may explain the variations in terms of resistance to chemotherapy or radiotherapy observed among different patients.…”