Expression of a G-protein {beta} subunit-related gene during lymphocyte activation

Using a subtractlve strategy, we have cloned an activation-relatedgene from a human B cell cDNA library. Sequence analysis revealedthat this gene was identical to H12.3, a gene belonging to anexpanding family of guanlne nucleotlde-blndlng protein ßsubunlts. The expression of H12.3 was induclble in the latephase of mltogen-stlmulated T and B cells. In T cells, IL-2and IL-4 by themselves had no direct effect on the expressionof H12.3, but they could augment the level of steady-state H12.3mRNA stimulated by phytohemagglutlnln. On the other hand, IFN-and IL-6 had no obvious effect on the expression in B cellswith or without Staphytococcus aureus Cowan l-stlmulatlon. CyclosporinA, a strong immunosuppressant, Inhibited the mltogen-stlmulatedexpression of H12.3, but rapamycin, another such agent, didnot. In synchronized Jurkat cells, the expression of H12.3 hadno cell cycle-dependent decrease in S and G₂/M phase, whilecyclin E, which controls the progression of the cell cycle unlate G₁ phase, did show a periodic expression pattern. The resultssuggest that H12.3 might be involved in regulation of lymphocyteactivation.