Multiple mRNA species with distinct 3' termini are transcribed from the beta 2-microglobulin gene.

beta 2-Microglobulin is the small, relatively invariant subunit of a family of cell-surface glycoproteins encoded within the major histocompatibility complex (MHC). Proteins associated with beta 2-microglobulin in the mouse include the classical transplantation antigens (H-2K, D and L), the thymus leukaemia antigen (TL) and certain haematopoietic cell differentiation antigens (Qa-1 and Qa-2). The genes encoding these proteins are members of a large, multigene family. In contrast, beta 2-microglobulin is encoded by a single copy gene on mouse chromosome 2 (refs 5, 6). We have shown that this gene consists of four coding blocks separated by three intervening sequences. We now demonstrate that the single beta 2-microglobulin gene is transcribed into at least two different size classes of mRNA that differ in the lengths of their 3' untranslated regions. We further show that three polyadenylation signals and a poly (A) tail are encoded at the 3' end of the gene.