title: Retroviral gag and DNA endonuclease coding sequences in IgE-binding factor gene.
abstract: Immunoglobulin-binding factors are known to regulate the synthesis of B-cell-derived immunoglobulin heavy-chain isotypes. Cloning and nucleotide sequence determination of complementary DNA encoding rodent IgE-binding factors (IgE-BF) revealed that messenger RNA encodes a glycoprotein of 557 amino acids which is expressed as a precursor of relative molecular mass (Mr) 60,000 (60K) in COS7 monkey cells. We report here that the 3' two-thirds of the IgE-BF coding sequence shows a surprising homology (72%) at the DNA level with coding sequences of the gag and pol (DNA endonuclease) genes of the Syrian hamster intracisternal A particle (IAP H18), an endogenous retrovirus. This marked homology demonstrates that the rodent gene encoding IgE-BF is a hybrid gene which evolved very recently by integrating genes of viral origin, and that the encoded polypeptide comprises three separate domains: an IgE-BF domain and retrovirus-derived gag and DNA endonuclease-like domains. This may represent the first report of a cellular gene containing a virus-derived coding sequence.
mesh_terms: D000818:Animals; D005075:Biological Evolution; D006224:Cricetinae; D003850:Deoxyribonuclease I / Q000235:genetics*; D015683:Gene Products, gag; D005814:Genes, Viral; D008222:Lymphokines / Q000235:genetics*; D029584:Prostatic Secretory Proteins; D012190:Retroviridae / Q000235:genetics*; D012191:Retroviridae Proteins / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid
chemical_list: D015683:Gene Products, gag; D008222:Lymphokines; D029584:Prostatic Secretory Proteins; D012191:Retroviridae Proteins; C043076:beta-microseminoprotein; C013059:immunoglobulin-binding factors; D003850:Deoxyribonuclease I