Release of RASSF1C from the nucleus by Daxx degradation links DNA damage and SAPK/JNK activation

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Abstract
Stress‐activated protein kinase/c‐Jun N‐terminal kinase (SAPK/JNK) responds to a variety of stress stimuli and controls cell fates such as cell cycle entrance, apoptosis and senescence. Stimuli such as ultraviolet irradiation and chemical reagents that damage genomic DNA induce the activation of the SAPK/JNK signaling pathway. However, it is unclear how the signal arising in the nucleus owing to DNA damage is transmitted to SAPK/JNK in the cytoplasm. Here, we report that the nuclear components Daxx and Ras‐association domain family 1C (RASSF1C) link DNA damage to SAPK/JNK activation in HeLa cells. In response to DNA damage, Daxx localized in promyelocytic leukaemia‐nuclear bodies (PML‐NBs) undergoes ubiquitination and degradation. RASSF1C, a tumor suppressor and newly identified binding partner of Daxx, is constitutively anchored by Daxx in PML‐NBs but is released from the nucleus when Daxx is degraded. This released RASSF1C translocates to cytoplasmic microtubules and participates in the activation of SAPK/JNK. Our data define a novel mechanism by which the Daxx–RASSF1C complex in PML‐NBs couples nuclear DNA damage to the cytoplasmic SAPK/JNK signaling pathway.