Highlights d TED-seq reveals the regulation of polyadenylation in ER stress response d Poly(A) lengths are increased in ER stress-induced mRNAs d Increased poly(A) lengths are linked to translation and stability in ER stress d mRNAs in stress-induced RNA-granule fraction have shorter poly(A) tails

Uncontrolled activation of FGFRs induces the progression of various cancers. It was recently reported that FGFR2-activating mutants are implicated in about 12% of endometrial carcinomas.

Aberrant mutational activation of FGFR2 is associated with endometrial cancers (ECs). AP24534 (ponatinib) currently undergoing clinical trials has been known to be an orally available multi-targeted tyrosine kinase inhibitor. Our biochemical kinase assay showed that AP24534 is potent against wild-type FGFR1-4 and 5 mutant FGFRs (V561M-FGFR1, N549H-FGFR2, K650E-FGFR3, G697C-FGFR3, N535K-FGFR4) and possesses the strongest kinase-inhibitory activity on N549H-FGFR2 (IC 50 of 0.5 nM) among all FGFRs tested. We therefore investigated the effects of AP24534 on endometrial cancer cells harboring activating FGFR2 mutations and explored the underlying molecular mechanisms. AP24534 significantly inhibited the proliferation of endometrial cancer cells bearing activating FGFR2 mutations (N549K, K310R/N549K, S252W) and mainly induced G1/S cell cycle arrest leading to apoptosis. AP24534 also diminished the kinase activity of immunoprecipitated FGFR2 derived from MFE-296 and MFE-280 cells and reduced the phosphorylation of FGFR2 and FRS2 on MFE-296 and AN3CA cells. AP24534 caused substantial reductions in ERK phosphorylation, PLCg signaling and STAT5 signal transduction on ECs bearing FGFR2 activating mutations. Akt signaling pathway was also deactivated by AP24534. AP24534 causes the chemotherapeutic effect through mainly the blockade of ERK, PLCg and STAT5 signal transduction on ECs. Moreover, AP24534 inhibited migration and invasion of endometrial cancer cells with FGFR2 mutations. In addition, AP24534 significantly blocked anchorage-independent growth of endometrial cancer cells. We, for the first time, report the molecular mechanisms by which AP24534 exerts antitumor effects on ECs with FGFR2 activating mutations, which would provide mechanistic insight into ongoing clinical investigations of AP24534 for ECs.

Enhancer RNAs (eRNA) are non-coding RNAs transcribed bidirectionally from active regulatory sequences. Their expression levels correlate with the activating potentials of the enhancers, but due to their instability, eRNAs have proven difficult to quantify in large scale. To overcome this, we use capped-nascent-RNA sequencing to efficiently capture the bidirectional initiation of eRNAs. We apply this in large scale to the human lymphoblastoid cell lines from the Yoruban population, and detected nearly 75,000 eRNA transcription sites with high sensitivity and specificity. We identify genetic variants significantly associated with overall eRNA initiation levels, as well as the transcription directionality between the two divergent eRNA pairs, namely the transcription initiation and directional initiation quantitative trait loci (tiQTLs and diQTLs) respectively. High-resolution analyses of these two types of eRNA QTLs reveal distinct positions of enrichment not only at the central transcription factor (TF) binding regions but also at the flanking eRNA initiation regions, both of which are equivalently associated with mRNA expression QTLs. These two regions -the central TF binding footprint and the eRNA initiation cores -define the bipartite architecture and the function of enhancers, and may provide further insights into interpreting the significance of non-coding regulatory variants.

Aberrant RET kinase signaling plays critical roles in several human cancers such as thyroid carcinoma. The gatekeeper mutants (V804L or V804M) of RET are resistant to currently approved RET inhibitors such as cabozantinib and vandetanib. We, for the first time, report a highly selective and extremely potent RET inhibitor, 6i rationally designed. Compound 6i inhibits strongly RET gatekeeper mutants and other clinically relevant RET mutants as well as wt-RET. This substance also significantly suppresses growth of thyroid cancer-derived TT cell lines and Ba/F3 cells transformed with various RET mutants. Docking studies reveal that the isoxazole moiety in 6i is responsible for binding affinity improvement by providing additional site for H-bonding with Lys758. Also, 6i not only substantially blocks cellular RET autophosphorylation and its downstream pathway, it markedly induces apoptosis and anchorage-independent growth inhibition in TT cell lines while having no effect on normal thyroid Nthy ori-3-1 cells.