KPC2 relocalizes HOXA2 to the cytoplasm and decreases its transcriptional activity

• Hoxa2 interacts with KPC2, an adapter protein of the KPC ubiquitin-ligase complex.
• KPC2 relocalizes Hoxa2 to the cytoplasm.
• KPC2 diminishes Hoxa2 transcriptional activity.
• KPC2 interaction is conserved among HOX proteins.
• Kpc2 and Hoxa2 expression patterns partially overlap in the early mouse embryo.

Regulation of transcription factor activity relies on molecular interactions or enzymatic modifications which influence their interaction with DNA cis-regulatory sequences, their transcriptional activation or repression, and stability or intracellular distribution of these proteins. Regarding the well-conserved Hox protein family, a restricted number of activity regulators have been highlighted thus far. In the framework of a proteome-wide screening aiming at identifying proteins interacting with Hoxa2, KPC2, an adapter protein constitutive of the KPC ubiquitin-ligase complex, was identified. In this work, KPC2 was confirmed as being a genuine interactor of Hoxa2 by co-precipitation and bimolecular fluorescence complementation assays. At functional level, KPC2 diminishes the transcriptional activity and induces the nuclear exit of Hoxa2. Gene expression analyses revealed that Kpc2 is active in restricted areas of the developing mouse embryo which overlap with the Hoxa2 expression domain. Together, our data support that KPC2 regulates Hoxa2 by promoting its relocation to the cytoplasm.