Enables RNA polymerase II transcription regulatory region sequence-specific DNA binding activity. Involved in several processes, including ATF6-mediated unfolded protein response; determination of adult lifespan; and endoplasmic reticulum calcium ion homeostasis. Predicted to be located in nucleus. Expressed in several structures, including intestine; muscle cell; pharyngeal gland cell; rectum; and vulva. Human ortholog(s) of this gene implicated in achromatopsia 7. Is an ortholog of human ATF6 (activating transcription factor 6) and ATF6B (activating transcription factor 6 beta).