A Cyclin-Dependent Kinase that Promotes Cytokinesis through Modulating Phosphorylation of the Carboxy Terminal Domain of the RNA Pol II Rpb1p Sub-Unit

In Schizosaccharomyces pombe, the nuclear-localized kinase, Lsk1p, promotes cytokinesis by positively regulating the Septation Initiation Network (SIN). Although a member of the cyclin-dependent kinase (CDK) family, neither a cyclin partner nor a physiological target has been identified. In this report we identify a cyclin, Lsc1p, that physically interacts and co-localizes with Lsk1p. Furthermore, lsk1Δ, lsc1Δ, as well as kinase-dead lsk1-K306R mutants, display highly similar cytokinesis defects. Lsk1p is related to CDKs that phosphorylate the carboxy-terminal domain (CTD) of the largest sub-unit of RNA polymerase II (Rpb1p). Interestingly, we find that Lsk1p and Lsc1p are required for phosphorylation of Ser-2 residues found in the heptad repeats of the CTD. To determine if Rpb1p could be a physiological target, we replaced the native rpb1 gene with a synthetic gene encoding a Rpb1p protein in which Ser-2 was substituted with the non-phosphorylatable amino-acid alanine in all heptads. Cells carrying this allele were similar to lsk1Δ mutants: They were viable, displayed genetic interactions with the SIN, and were unable to complete cytokinesis upon perturbation of the cell division machinery. We conclude that Ser-2 phosphorylation of the CTD heptads plays a novel physiological role in the regulation of cytokinesis

FIGHT-302: first-line pemigatinib vs gemcitabine plus cisplatin for advanced cholangiocarcinoma with FGFR2 rearrangements

FGFR2 rearrangements resulting in dysregulated signaling are drivers of cholangiocarcinoma (CCA) tumorigenesis, and occur almost exclusively in intrahepatic CCA. Pemigatinib, a selective, potent, oral inhibitor of FGFR1-3, has demonstrated efficacy and safety in a Phase II study of patients with previously treated locally advanced/metastatic CCA harboring FGFR2 fusions/rearrangements. We describe the study design of FIGHT-302, an open-label, randomized, active-controlled, multicenter, global, Phase III study comparing the efficacy and safety of first-line pemigatinib versus gemcitabine plus cisplatin in patients with advanced CCA with FGFR2 rearrangements (NCT03656536). The primary end point is progression-free survival; secondary end points are objective response rate, overall survival, duration of response, disease control rate, safety and quality of life