Unexpected functional role of the transactivation domain for nuclear import of STAT5
The transactivation domain of STAT5 plays a crucial role in its nuclear import following Epo stimulation, with specific amino acids identified as essential for this process.
Where it sits
this study against the rest of the erythropoietin (epo) corpusSummary and findings
This study investigates the role of the transactivation domain (TAD) in the nuclear import of STAT5 in HeLa EpoR cells. The researchers found that STAT5 mutants lacking the TAD were retained in the cytoplasm after Epo stimulation. A specific 12-amino-acid stretch within the TAD was identified as sufficient for restoring nuclear translocation.
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.