LncFALEC recruits ART5/PARP1 and promotes castration-resistant prostate cancer through enhancing PARP1-meditated self PARylation.

Accumulating evidence indicates that long noncoding RNAs (lncRNAs) are abnormal expression in various malignant tumors. Our previous research demonstrated that focally amplified long non-coding RNA (lncRNA) on chromosome 1 (FALEC) is an oncogenic lncRNA in prostate cancer (PCa). However, the role of FALEC in castration-resistant prostate cancer (CRPC) is poorly understood. In this study, we showed FALEC was upregulated in post-castration tissues and CRPC cells, and increased FALEC expression was associated with poor survival in post-castration PCa patients. RNA FISH demonstrated FALEC was translocated into nucleus in CRPC cells. RNA pulldown and followed Mass Spectrometry (MS) assay demonstrated FALEC directly interacted with PARP1 and loss of function assay showed FALEC depletion sensitized CRPC cells to castration treatment and restored NAD(+). Specific PARP1 inhibitor AG14361 and NAD(+) endogenous competitor NADP(+) sensitized FALEC-deleted CRPC cells to castration treatment. FALEC increasing PARP1 meditated self PARylation through recruiting ART5 and down regulation of ART5 decreased CRPC cell viability and restored NAD(+) through inhibiting PARP1meditated self PARylation in vitro. Furthermore, ART5 was indispensable for FALEC directly interaction and regulation of PARP1, loss of ART5 impaired FALEC and PARP1 associated self PARylation. In vivo, FALEC depleted combined with PARP1 inhibitor decreased CRPC cell derived tumor growth and metastasis in a model of castration treatment NOD/SCID mice. Together, these results established that FALEC may be a novel diagnostic marker for PCa progression and provides a potential new therapeutic strategy to target the FALEC/ART5/PARP1 complex in CRPC patients.