Kinase Activation and Transformation by NUP214-ABL1 Is Dependent on the Context of the Nuclear Pore

Abstract

Genetic alterations causing constitutive tyrosine kinase activation are observed in a broad spectrum of cancers. Thus far, these mutant kinases have been localized to the plasma membrane or cytoplasm, where they engage proliferation and survival pathways. We report that the NUP214-ABL1 fusion is unique among these because of its requisite localization to the nuclear pore complex for its transforming potential. We show that NUP214-ABL1 displays attenuated transforming capacity as compared to BCR-ABL1 and that NUP214-ABL1 preferentially transforms T cells, which is in agreement with its unique occurrence in T cell acute lymphoblastic leukemia. Furthermore, NUP214-ABL1 differs from BCR-ABL1 in subcellular localization, initiation of kinase activity, and signaling and lacks phosphorylation on its activation loop. In addition to delineating an unusual mechanism for kinase activation, this study provides new insights into the spectrum of chromosomal translocations involving nucleoporins by indicating that the nuclear pore context itself may play a central role in transformation.

Intrinsic differences between the catalytic properties of the oncogenic NUP214-ABL1 and BCR-ABL1 fusion protein kinases

“…4,33,34 Whereas phosphorylation of Tyr-412 is required to stabilize the activation loop in an open conformation and is associated with high catalytic output, phosphorylation on Tyr-245 appears to stabilize an active kinase conformation by interfering with the autoinhibitory binding of the SH3 domain to the SH2-kinase domain linker. As previously published, although Tyr-245 is 24 also data not shown). These results indicated that both NUP214-ABL1 and BCR-ABL1 are constitutively active tyrosine kinases, but the differences in phosphorylation pattern argue that NUP214-ABL1 is a weaker kinase than BCR-ABL1.…”

“…24,27 Finally, NUP214-ABL1 has attenuated transforming capacity as compared with BCR-ABL1 and preferentially transforms T cells, which is in agreement with its unique occurrence in T-cell ALL. 24 On the basis of these observations, we have performed a thorough comparison of NUP214-ABL1 and BCR-ABL1 to highlight the unique biochemical properties of NUP214-ABL1 and to gain mechanistic insight in the different disease phenotypes caused by these two oncoproteins. Besides absent activation loop phosphorylation, we show that NUP214-ABL1 displays much lower general tyrosine autophosphorylation, higher Michaelis-Menten constant (K M ) and lower relative maximum velocity (V max ) values than BCR-ABL1.…”

“…HEK293 cells were grown in DMEM/F12 medium þ 10% fetal calf serum. Ba/F3 cells expressing BCR-ABL1 or NUP214-ABL1 were described previously 24 and were grown in RPMI-1640 þ 10% fetal calf serum.…”

“…Moreover, whereas all other ABL1 fusion kinases are localized to the cytoplasm or cortical actin cytoskeleton, NUP214-ABL1 is localized to the nuclear pore complex and is strictly dependent on this subcellular localization for its activity and oncogenic transformation. 24,25 In addition, NUP214-ABL1 lacks a direct binding site for the adaptor protein GRB2 that was shown to contribute to transformation and leukemogenesis of BCR-ABL1 and TEL-ABL1 12,14,15,26 and lacks phosphorylation of its activation loop (Tyr-412). 24,27 Finally, NUP214-ABL1 has attenuated transforming capacity as compared with BCR-ABL1 and preferentially transforms T cells, which is in agreement with its unique occurrence in T-cell ALL.…”

“…24,25 In addition, NUP214-ABL1 lacks a direct binding site for the adaptor protein GRB2 that was shown to contribute to transformation and leukemogenesis of BCR-ABL1 and TEL-ABL1 12,14,15,26 and lacks phosphorylation of its activation loop (Tyr-412). 24,27 Finally, NUP214-ABL1 has attenuated transforming capacity as compared with BCR-ABL1 and preferentially transforms T cells, which is in agreement with its unique occurrence in T-cell ALL. 24 On the basis of these observations, we have performed a thorough comparison of NUP214-ABL1 and BCR-ABL1 to highlight the unique biochemical properties of NUP214-ABL1 and to gain mechanistic insight in the different disease phenotypes caused by these two oncoproteins.…”