iASPP: Lysates

ASPP proteins (ASPP1, ASPP2 and iASPP) represent a new family of p53 binding proteins. ASPP1 and ASPP2 bind and enhance p53-mediated apoptosis. In contrast, the third member, iASPP, functionally inactivates p53. iASPP (also called protein phosphatase 1 regulatory (inhibitor) subunit 13 like protein, Inhibitor of ASPP protein, Protein iASPP, PPP1R13B-like protein and NFkB-interacting protein 1) plays a central role in regulation of apoptosis and transcription via its interaction with NF-kappa-B and p53/TP53 proteins. iASPP blocks transcription of HIV-1 virus by inhibiting the action of both NF-kappa-B and SP1. This protein also inhibits p53/TP53 function, possibly by preventing the association between p53/TP53 and ASPP1 or ASPP2, and therefore suppressing the subsequent activation of apoptosis. iASPP is predominantly a cytoplasmic protein (isoform 1) but can also be found in the nucleus (isoform 2). iASPP is highly expressed in heart, placenta and prostate and is weakly expressed in brain, liver, skeletal muscle, testis and peripheral blood leukocyte. The N-terminal region of isoform 1 is required for cytoplasmic localization. Defects in iASPP may be a cause of certain breast cancers and the protein is overexpressed in many patients suffering from breast carcinomas and expressing a wild-type p53/TP53 protein.