The invention provides DNA demethylases comprising Elp1, Elp2, Elp3, Elp4, Elp5 and/or Elp6. The invention also provides methods of modulating gene expression, for example, for the treatment of cancer or to modify the cellular transcription program (e.g., for regenerative medicine). Also provided are methods of identifying compounds that modulate the DNA demethylase activity of the DNA demethylases of the invention.