VIR_N is the conserved N-terminus of the protein virilizer, necessary for male and female viability and required for the production of eggs capable of embryonic development [1].

1: Molecular identification of virilizer, a gene required for the expression of the\tsex-determining gene Sex-lethal in Drosophila melanogaster. Niessen M, Schneiter R, Nothiger R; Genetics. 2001;157:679-688. PMID:11156988