U2-snRNP B" protein gene is an early growth-inducible gene.

In this work we isolated mouse U2-snRNP-specific b" clones and analysed the expression of the mouse U2-snRNP-specific b" and U1-snRNP-specific 70K genes in NIH-3T3 fibroblasts. Stimulation of growth-arrested NIH-3T3 cells with serum was found to evoke a rapid increase in the amount of cytoplasmic b" and 70K mRNAs. These increases in mRNA did not require de novo protein synthesis. Moreover, the inhibition of protein synthesis by cycloheximide caused a superinduction in the amounts of the U1-snRNP-specific 70K transcripts. We also found that c-Ha-rasVal12 oncogene-transformed NIH-3T3 cells have higher levels of the b" and 70K mRNAs than the normal 3T3 cells. These data imply that the b" and 70K are early growth response genes, and their enhanced expression might be of significance in the processing of pre-mRNAs into mature mRNAs.