부산대학교 도서관

Activation of murine splenic B lymphocytes with various mitogens was found to be associated with a prominent increase in synthesis and abundance of a 40 KDa/pI 5.0 nuclear protein (p40). Subcellular fractionation revealed that this protein is not found in the cytosol fraction and cannot be solubilized by DNAse or RNAse digestion, indication that the protein is mainly associated with the nuclear matrix. The increase in synthesis of p40 was detected at early G1 phase, 60 min following activation of the cells by the mitogen, reached a peak at 16h and declined to control level at 48h (during S phase). Activation of the cells with non mitogenic stimuli such as BSF-1, A23187, and PMA, induced an increase in synthesis of discrete nuclear proteins, but failed to affect the synthesis of p40, suggesting that the increase in synthesis of p40 is specifically associated with the signal of mitogenic stimuli but not with this of non mitogenic stimuli. Inhibition of the mitogenic effect of anti-Ig by PMA treatment of the cells was associated with specific inhibition in the synthesis of p40, while overcoming this inhibition by addition of 8-mercaptoguanosine was associated with restoration of the mitogenic effect of anti-Ig. These results suggest that p40 may have an important role in early induction of mitogenesis in B cells.