Mouse ING1 homologue, a protein interacting with A1, enhances cell death and is inhibited by A1 in mammary epithelial cells.

We cloned mouse ING1 homologue (mINGh), an A1/Bfl-1-interacting protein, from mouse mammary glands using a yeast two-hybrid assay and unexpectedly found four splicing variants of mINGh by reverse transcription-PCR assay and sequence analysis. The alternative splicing variants were mINGh-S, mINGh-M, mINGh-L, and mINGh-L2 encoding 171, 248, 166, and 227 amino acids, respectively. Cell death of HC11 cells, induced by serum starvation, was enhanced by mINGhs, and the action of mINGhs was inhibited by A1 protein. These results indicate that A1 can inhibit cell death not only via the well known pathway related to the Bcl-2 family but also through direct interaction with mINGh in mammary epithelial cells.