Progesterone Immunomodulatory Binding Factor 1 (PIBF1)

PIBF encodes a predicted hydrophilic 757-amino acid alpha-helical protein with an N-terminal signal sequence, a nuclear localization signal, a leucine zipper motif, a basic zipper sequence, a PEST sequence, an endoplasmic reticulum membrane retention signal, and several potential N-glycosylation and phosphorylation sites. Immunoblot analysis, immunocytochemistry, and fluorescence microscopy of insulin-treated mammary carcinoma cells detected expression of a 34-kD secreted protein in cytoplasmic granules. In untreated cells, nucleus-associated expression of the full-length 90-kD protein was detected.PIBF1 contains 758 amino acids. multiple PIBF1 transcripts expressed at highest levels in testis. Moderate expression was detected in spleen, thymus, prostate, ovary, small intestine, and colon.