Interacting selectively and non-covalently with a specific DNA sequence that is in cis with and relatively close to a core promoter for RNA polymerase II (RNAP II) and interacting selectively and non-covalently with copper(I) (Cu+) ion(s) and responding, e.g. by conformational change, to changes in the cellular level of copper(I) (Cu+), such a way that copper ion binding regulates the activity of the transcription factor, perhaps by regulating the ability to interact selectively and non-covalently with a sequence of DNA that is in cis with and relatively close to a core promoter for RNA polymerase II (RNAP II), or by regulating some other function of the transcription factor, in order to modulate transcription by RNAP II.