A construct pRL-rhTNF alpha 2, in which the 110 bp 3'-untranslated region of rhTNF alpha cDNA was deleted, was transformed in E.coli. The expression level of several positive transformants was determined. The results showed that the expression of pRL-TNF alpha 2 was stable and the biological characteristics of the protein product were the same as that of pRL-rhTNF alpha. Furthermore, the expression level of pRL-rhTNF alpha 2 was increased. It is suggested that the 3'-untranslated region may have some effects on gene expression. A TA-rich sequence, TTTATTA, contained in the 3'-untranslated region of pRL-rhTNF alpha may be involved in the inhibitory effect on gene expression.