Enables several functions, including promoter-specific chromatin binding activity; transcription coactivator activity; and transcription corepressor activity. Involved in several processes, including animal organ development; mRNA transcription by RNA polymerase II; and negative regulation of transcription by RNA polymerase II. Acts upstream of or within several processes, including animal organ development; cellular response to hepatocyte growth factor stimulus; and regulation of signal transduction. Located in nucleus. Part of mediator complex. Is expressed in several structures, including alimentary system; central nervous system; genitourinary system; hemolymphoid system gland; and lung. Used to study congestive heart failure and dilated cardiomyopathy. Orthologous to human MED1 (mediator complex subunit 1). [provided by Alliance of Genome Resources, Apr 2022]