Structure and Expression of Hemolin, an Insect Member of the Immunoglobulin Gene Superfamily

Abstract

Hemolin is an insect protein which belongs to the immunoglobulin superfamily and is strongly induced upon bacterial infection. It has been isolated from two moths, Hyalophora cecropia and Manduca sexta. We have isolated and sequenced a genomic clone for hemolin in H. cecropia, in order to resolve its organization and as a basis for investigating hemolin gene regulation. According to Southern-blot analysis, hemolin is encoded by a single gene, Hemolin. It contains six exons ranging over 32-603 bp. The introns are positioned both within and between the immunoglobulin-like domains, a feature typical for cell-adhesion molecules belonging to the immunoglobulin superfamily. By an RNase protection assay, we show that the Hemolin transcript is strongly induced not only by bacteria, but also by lipopolysaccharide and phorbol 12-myristate 13-acetate. Analysis of the upstream region and introns revealed potential binding sites for the Cecropia immunoresponsive factor (CIF), which recognizes the kappa B-like consensus GGGRA YYYYY.