After Ctr1-mediated cell uptake, copper (Cu) is transported by the cytoplasmic Cu chaperone
Atox1 to P1B type ATPases ATP7A and ATP7B in the Golgi network, for incorporation into Cudependent
enzymes. Atox1 is a small 68-residue protein that binds Cu in a conserved CXXC motif; it delivers
Cu to target domains in ATP7A/B via direct protein-protein interactions. Specific transcription factors
regulating expression of the human Cu transport proteins have not been reported although Atox1 was
recently suggested to have dual functionality such that it, in addition to its cytoplasmic chaperone function,
acts as a transcription factor in the nucleus. To examine this hypothesis, here we investigated the localization
of Atox1 in HeLa cells using fluorescence imaging in combination with in vitro binding experiments
to fluorescently labeled DNA duplexes harboring the proposed promotor sequence. We found that whereas Atox1
is present in the nucleus in HeLa cells, it does not bind to DNA in vitro. It appears that Atox1 mediates transcriptional regulation
via additional (unknown) proteins.
Keywords: Atox1, Copper chaperone, fluorescence microscopy, fluorescence spectroscopy, transcription factor.
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