The tissue specific SmN protein does not influence the alternative splicing of endogenous N-Cam and C-SRC RNAs in transfected 3T3 cells

The SmN protein is closely related to the constitutively expressed RNA splicing protein SmB but is expressed only in brain and heart tissue. The inclusion of the VASE exon in the N-Cam and mRNA and of the N1 exopn in the c-src mRNA correlates with the pattern of SmN, being observed in brain and heart but not in other tissues and increasing in amount as SmN levels increase during brain development. However, the artificial expression of SmN in cells in which it is normally absent does not affect the pattern of N-Cam and c-src splicing whilst a cell line lacking detectable SmN is able to include the VASE exon. Hence SmN does not appear to be necessary or sufficient for these tissue-specific and developmentally regulated alternative splicing events.