ALTERNATIVE SPLICING GIVES RISE TO 2 NOVEL LONG ISOFORMS OF ZN-ALPHA(2)-GLYCOPROTEIN, A MEMBER OF THE IMMUNOGLOBULIN SUPERFAMILY

We have isolated, from a rat liver cDNA library, two cDNAs encoding no vel long isoforms of Zn-alpha(2)-glycoprotein (Zn-alpha(2)-gp), a memb er of the immunoglobulin superfamily with a high degree of sequence si milarity to class-I major histocompatibility complex (MHC) antigens. N ucleotide (nt) sequence analysis of these two novel cDNAs has revealed that they contain insertions of 138 and 123 nt between the second and third exons of Zn-alpha(2)-gp, resulting in in-frame insertions of 46 and 41 amino acids (aa), respectively. Analysis of the mechanism of g eneration of both isoforms, named Zn-alpha(2)-gpA and Zn-alpha(2)-gpB, has shown that they result from a series of alternative splicing even ts, including alternative use of two additional exons, and of two diff erent 3'-splice sites present in the first of these novel exons, The o ccurrence of these alternative splicing events in Zn-alpha(2)-gp could contribute to increasing the diversity of this nonpolymorphic and sol uble class-I MHC antigen.