Dimerization of two novel apoptosisinducing proteins and its function in regulating cell apoptosis

Asy (apoptosis/saibousi Yutsudo) is a novel apoptosis-inducing gene found in 1999 by Yutsudo group in Japan. In 2000, Qi Bing et al. cloned another novel gene, named hap (homologue of ASY protein), which encoded the ASY interact ing protein, from human lung cell line (WI-38) cDNA library by using yeast two-h ybrid system. It has been proved that ASY formed homodimer in yeast and human ce ll line, ASY and HAP formed heterodimer in yeast cells, and both induced cell ap optosis in human tumor cell lines Sao2 and CGL4. This paper showed that HAP coul d form homodimer in yeast cells by yeast two-hybrid system; HAP and ASY could pr oduce heterodimer in human cell line by cross-immunoprecipitation test; by using apoptosis-testing technologies such as AnnexinV, TUNEL, DNA ladder and Flow Cyt ometry, the cell apoptosis in human normal or tumor cell lines transfected with hap or asy individually or cotransfected by the both was qualified or quantified . It was firstly demonstrated that ASY or HAP induced cell apoptosis not only in human tumor cell lines, but also in human normal cell lines. Moreover, we prove d that the heterodimer between ASY and HAP decreased apoptosis-inducing activity from the homodimer of ASY or HAP. It revealed that by choosing to form heterodi mer or homodimer between ASY and / or HAP is an important mechanism of regulatin g apoptosis in human cell lines.