We report a previously uncharacterized alpha-helical module, the BEN domain, in diverse animal proteins such as BANP/SMAR1, NAC1 and the Drosophila mod(mdg4) isoform C, in the chordopoxvirus virosomal protein E5R and in several proteins of polydnaviruses. Contextual analysis suggests that the BEN domain mediates protein-DNA and protein-protein interactions during chromatin organization and transcription. The presence of BEN domains in a poxviral early virosomal protein and in polydnaviral proteins also suggests a possible role for them in organization of viral DNA during replication or transcription.