Enables DNA-binding transcription repressor activity, RNA polymerase II-specific and RNA polymerase II cis-regulatory region sequence-specific DNA binding activity. Involved in SMAD protein signal transduction; cellular response to BMP stimulus; and regulation of transcription by RNA polymerase II. Acts upstream of or within several processes, including animal organ development; osteoblast fate commitment; and transmembrane receptor protein serine/threonine kinase signaling pathway. Located in cytoplasm and nucleus. Is expressed in several structures, including alimentary system; brain; egg cylinder; embryo mesenchyme; and genitourinary system. Orthologous to human SMAD5 (SMAD family member 5). [provided by Alliance of Genome Resources, Apr 2022]