In order to study whether there is a functional regulation region within the 3��untranslational region (UTR) of human phosphoinositide 3 kinase��(PI3K��)mRNA, the 3��UTR was analyzed through bioinformatics. An AU rich region (AUR)of about 0 9 kb was found. Within the AU rich region there are 4 AU rich elements (AREs) and a region which is homologous with many other UTRs. The AU rich region was inserted into the 3��UTR of egfp reporter gene, and pcDNA3 egfp AUR expressing vector was constructed. The expression of egfp containing the 3��UTR of PI3K�� was significantly reduced by 2��3 times in NIH 3T3, 7402 and K562 cells. After treated with actinomycin D (5 ��g/ml) total RNA from stably transfected K562 cells were successively extracted with an interval of 2 hours, and the stability of egfp mRNA was analyzed through Northern blotting. The result showed that the AU rich region of PI3K�� could, to some extent, accelerate the decay of egfp mRNA. These results indicate that there is probably a negative regulation region within the 3��AU rich region of PI3K�� mRNA 3��UTR.