Effects of intron length on differential processing of mouse mu heavy-chain mRNA.

Production of membrane-bound and secreted forms of mouse mu heavy-chain mRNA is controlled by differential processing in a developmental-stage-specific manner. We have analyzed the effects of various deletions and insertions in the C4-M1 intron of the mouse mu gene on the differential processing of mu mRNA. We show that there is a correlation between the length of the C4-M1 intron and the molar ratio of membrane-bound to secreted mu mRNAs, i.e., the shorter the C4-M1 intron, the higher the ratio. Since the poly(A) addition signal in the C4-M1 intron seems to be intact in the mutant mu genes, it is likely that the efficiency of splicing of the C4-M1 intron is affected by changes in the intron length.