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bioRxiv · 10.64898/2025.12.11.693681

Unexpected functional role of the transactivation domain for nuclear import of STAT5

Ernst, S.·Borgen-Moller, M.·Kuster, A.·Schurse, H.·Muller-Newen, G.
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Abstract

Signal transducer and activator of transcription 5 (STAT5) is a key transcriptional regulator acting downstream of hematopoietic cytokines and hormones, such as erythropoietin (Epo), thrombopoietin or prolactin. STAT5-mediated gene regulation involves tyrosine phosphorylation at cytokine receptors and subsequent nuclear import. We studied STAT5 nucleocytoplasmic shuttling via live-cell imaging of fluorescent mutants in STAT5-/- HeLa EpoR cells. Unexpectedly, STAT5 mutants lacking the transactivation domain (TAD) were retained in the cytoplasm following Epo stimulation. Building upon this, we identified a 12-amino-acid stretch in the TAD sufficient to restore nuclear translocation. Further analysis revealed two residues within this 12-amino-acid stretch, D754 and D758, to be essential for nuclear import of phosphorylated full-length STAT5. Importantly, a single intact TAD in the STAT5 dimer is sufficient for nuclear import. Our findings reveal a unique role of the TAD in STAT5 nuclear trafficking distinct from other STATs, providing new mechanistic insight and potential targets for therapeutic intervention in STAT5-driven disease such as myeloproliferative neoplasms and leukemia.

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Ernst, S., Borgen-Moller, M., Kuster, A., Schurse, H., Muller-Newen, G.. 2025-12-14. Unexpected functional role of the transactivation domain for nuclear import of STAT5. https://doi.org/10.64898/2025.12.11.693681

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