AMY-1, a c-Myc-binding protein, is localized in the mitochondria of sperm by association with S-AKAP84, an anchor protein of cAMP-dependent protein kinase

We have reported that a novel c-Myc-binding protein, AMY-1 (Associate of My c-1), stimulated the transcription activity of c-Myc. To access the molecul ar function of AMY-1, a two-hybrid screening of cDNAs encoding AMY-1-bindin g proteins was carried out with AMY-1 as a bait using a human HeLa cDNA lib rary, and a clone encoding cAMP-dependent protein kinase anchor protein 149 (AKAP149), was obtained. AMY-1 was found to bind in vitro and in vivo to t he regulatory subunit II binding region of AKAP149 and S-AKAP84, a splicing variant of AKAP149 expressed in the testis. AMY-1 was expressed postmeioti cally in the testis, as S-AKAP84 was expressed. Furthermore, S-AKAP84 and r egulatory subunit II, a regulatory subunit of cAMP-dependent protein kinase , made a ternary complex in cells, and AMY-I was localized in the mitochond ria of HeLa and sperm in association with AKAP149 and S-AKAP84, respectivel y. These results suggest that AMY-1 plays a role in spermatogenesis.