Recent studies have shown that a subset of nucleoporins (Nups) can detach from the nuclear pore complex and move into the nuclear interior to regulate transcription. One such dynamic Nup, called Nup98, has been implicated in gene activation in healthy cells and has been shown to drive leukemogenesis when mutated in patients with acute myeloid leukemia (AML). Here we show that in hematopoietic cells, Nup98 binds predominantly to transcription start sites to recruit the Wdr82–Set1A/COMPASS (complex of proteins associated with Set1) complex, which is required for deposition of the histone 3 Lys4 trimethyl (H3K4me3)-activating mark. Depletion of Nup98 or Wdr82 abolishes Set1A recruitment to chromatin and subsequently ablates H3K4me3 at adjacent promoters. Furthermore, expression of a Nup98 fusion protein implicated in aggressive AML causes mislocalization of H3K4me3 at abnormal regions and up-regulation of associated genes. Our findings establish a function of Nup98 in hematopoietic gene activation and provide mechanistic insight into which Nup98 leukemic fusion proteins promote AML.

Triggering of cAMP and mitogen-activated (MAPK) pathways in response to hormonal and growth factor cues promotes melanocyte pigmentation and survival in part through induction of the master regulator MITF by the cAMP-responsive factor CREB. We examined the role of CREB coactivators (CRTC1-3) in transduction of cAMP and MAPK signals in melanocytes. We found that knockout of the CRTC3 gene in mice and B16F1 melanoma cells decreases pigmentation by directly regulating the expression of the melanosomal transporter OCA2. In addition to effects of cAMP, CRTC3 activation was also promoted by ERK1/2-mediated phosphorylation at Ser391; amounts of phosphorylated CRTC3-S391 were constitutively elevated in human melanoma cells expressing mutated BRAF or NF1. Knockout of CRTC3 in A375 melanoma cells impaired their anchorage-independent growth, migration and invasiveness, whereas CRTC3 over-expression increased survival in response to BRAF inhibition by vemurafenib. Analysis of spontaneous CRTC3 mutations in melanomas reveals that increased activity of this co-activator is associated with reduced patient survival. Our results highlight the importance of CRTC3 in pigmentation and melanoma progression.