Telomerase-negative tumors can maintain telomere length by alternative lengthening of telomeres (ALT) but the mechanism behind ALT is poorly understood. Aggressive Neuroblastoma (NB), in particular, relapsed tumors are positive for ALT (ALT+) which suggests that better dissection of the ALT mechanism could provide novel therapeutic opportunities. TERRA long non-coding RNA (lncRNA) which is derived from the telomere ends is localized to telomeres in R-loop dependent manner and is essential for telomere maintenance. In the present study, we provide evidence that RNA modification at the N6 position of internal adenosine (m6A) in TERRA RNA by methyltransferase METTL3 is essential for telomere maintenance in ALT+ cells and that loss of TERRA m6A/METTL3 leads to telomere damage. We observed that R-loop enriched TERRA is abundantly m6A modified and m6A mediated recruitment of hnRNPA2B1 to TERRA RNA is essential for R-loop formation. Our data suggest that m6A drives telomere targeting of TERRA via R-loop and this m6A mediated R-loop formation could be a widespread mechanism utilized by other chromatin-interacting lncRNAs. Furthermore, treating ALT+ NB cells with METTL3 inhibitor leads to compromised telomere targeting of TERRA and accumulation of DNA damage over telomere, suggesting METTL3 inhibition could be a therapeutic opportunity for ALT+ NB.

Activated Cdc42-associated kinase (ACK) is a Rho family effector that is widely implicated in cancer. Here, we describe new roles for ACK in transcriptional regulation mediated by its relationship with the signal transducer and activators of transcription (STAT) family. We show that ACK can interact with STAT3, STAT5A and STAT5B, and augments phosphorylation at the conserved activation tyrosine on these STAT members. ACK stimulates oncogenic STAT nuclear relocation and transcriptional activation. We also identify endogenous relationships between ACK and STAT family members in haematopoietic disease cell lines. In the K562 chronic myeloid leukaemia cell line, we confirm that ACK contributes to the pool of active, nuclear STAT5. By interrogating ACK knock out cells we describe an ACK-driven STAT5 transcriptional signature in K562s. We propose ACK as a contributor to hyperactivated STAT5 signalling in this CML cell line and reveal a new route for therapeutic intervention.