Mael is essential for cancer cell survival and tumorigenesis through protection of genetic integrity

// Su-Hyeon Kim 1 , Eun-Ran Park 1 , Eugene Cho 1 , Won-Hee Jung 1 , Ju-Yeon Jeon 1 , Hyun-Yoo Joo 1 , Kee-Ho Lee 1 , Hyun-Jin Shin 1 1 Division of Radiation Cancer Research, Korea Institute of Radiological & Medical Sciences, Seoul 139-706, Republic of Korea Correspondence to: Kee-Ho Lee, email: khlee@kirams.re.kr Hyun-Jin Shin, email: hjshin@kirams.re.kr Keywords: Mael, oncogenic transformation, genetic integrity, oncogene, ATM Received: May 02, 2016      Accepted: November 21, 2016      Published: December 01, 2016 ABSTRACT Germ line-specific genes are activated in somatic cells during tumorigenesis, and are accordingly referred to as cancer germline genes. Such genes that act on piRNA (Piwi-interacting RNA) processing play an important role in the progression of cancer cells. Here, we show that the spermatogenic transposon silencer maelstrom (Mael), a piRNA-processing factor, is required for malignant transformation and survival of cancer cells. A specific Mael isoform was distinctively overexpressed in diverse human cancer cell lines and its depletion resulted in cancer-specific cell death, characterized by apoptosis and senescence, accompanied by an increase in reactive oxygen-species and DNA damage. These biochemical changes and death phenotypes induced by Mael depletion were dependent on ATM. Interestingly Mael was essential for Myc/Ras-induced transformation, and its overexpression inhibited Ras-induced senescence. In addition, Mael repressed retrotransposon activity in cancer cells. These results suggest that Mael depletion induces ATM-dependent DNA damage, consequently leading to cell death specifically in cancer cells. Moreover, Mael possesses oncogenic potential that can protect against genetic instability.