Two mRNAs with different 3′ ends encode membrane-bound and secreted forms of immunoglobulin μ chain

J Rogers, P Early, C Carter, K Calame, M Bond, L Hood… - Cell, 1980 - cell.com
J Rogers, P Early, C Carter, K Calame, M Bond, L Hood, R Wall
Cell, 1980cell.com
During differentiation, B lymphocytes undergo a shift from expression of membrane-bound
IgM to IgM secretion. The p chains of membrane and secreted IgM, CL,,, and cs,
respectively, differ in the amino acid sequence of their carboxy terminal regions. In this
paper, we demonstrate that pm and ps heavy chains. are encoded by separate mRNAs of
2.7 and 2.4 kb, respectively. Restriction mapping and sequence analysis of p cDNA clones
from a myeloma tumor that produces both types of p chain indicate that the pm and ps …
Summary
During differentiation, B lymphocytes undergo a shift from expression of membrane-bound IgM to IgM secretion. The p chains of membrane and secreted IgM, CL,,, and cs, respectively, differ in the amino acid sequence of their carboxy terminal regions. In this paper, we demonstrate that pm and ps heavy chains. are encoded by separate mRNAs of 2.7 and 2.4 kb, respectively. Restriction mapping and sequence analysis of p cDNA clones from a myeloma tumor that produces both types of p chain indicate that the pm and ps mRNAs are identical throughout the coding region up to the 3’end of the fourth constant region (C, 4) domain, but differ in their C terminal coding and 3’untranslated segments. From the nucleotide sequence of the p,,, cDNA clone, we predict the amino acid sequence of the 41-residue P,,, C terminal segment or “M”(membrane) segment. This sequence has characteristics consistent with its being a transmembrane peptide. Thus the cs chain has a 2D-residue hydrophilic C terminal segment after the C&4 domain, and the CL,,, chain has a 41-residue C terminal segment containing a hydrophobic sequence. We propose that comparable C terminal segments also will be found in other membrane-bound immunoglobulin heavy chains.
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