Structure of a pseudokinase-domain switch that controls oncogenic activation of Jak kinases

Area of Science:

• Biochemistry
• Molecular Biology
• Oncology

Background:

• The V617F mutation in Janus kinase 2 (Jak2) is a key driver of myeloproliferative neoplasms.
• The analogous V658F mutation in Janus kinase 1 (Jak1) is implicated in T-cell leukemias.
• Understanding the structural and functional consequences of these mutations is crucial for developing targeted therapies.

Purpose of the Study:

• To elucidate the structural basis of V658F-mutant human Jak1 pseudokinase activity.
• To investigate the role of a specific linker segment (encoded by exon 12) in Jak1 and Jak2 function.
• To determine if the observed conformational changes are conserved and contribute to oncogenic signaling.

Main Methods:

• X-ray crystallography was used to determine the structures of wild-type and V658F-mutant human Jak1 pseudokinase.
• Comparative structural analysis was performed between Jak1 and Jak2 structures.
• Bioinformatic tools were employed to analyze the conformational switch and linker remodeling.

Main Results:

• Crystal structures revealed a significant conformational switch in the V658F-mutant Jak1 pseudokinase.
• This switch involves a remodeling of a linker segment encoded by exon 12, a known mutation hotspot in Jak2.
• The identified conformational change is structurally conserved with the V617F mutation in Jak2.

Conclusions:

• The V658F mutation in Jak1 induces a conformational switch that remodels the exon 12-encoded linker segment.
• This structural remodeling is analogous to the mechanism observed in V617F-mutant Jak2.
• The conformational switch is essential for V617F-mediated Jak2 activation and may play a role in normal Jak activation pathways.