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Description

Pituitary-specific positive transcription factor 1 (UniProt P28069, also known as GHF-1, Growth hormone factor 1, PIT-1) is encoded by the POU1F1 (also known as CPHD1, GHF1, PIT1) gene (Gene ID 5449) in human. PIT-1 is a transcription factor that serves as a master regulator of lineage commitment and expansion during the anterior pituitary development process that drives regional expansion and functional differentiation of five distinct hormone-producing cell lineages, including somatotropes, lactotropes, thyrotropes, corticotropes, and gonadotropes. Loss of Pit-1 expression results in a combined pituitary hormone deficiency (CPHD) syndrome reflecting the absence of lactotropes, somatotropes, and a subset of thyrotropes. Although originally characterized as pituitary-specific, PIT-1 is also expressed in human breast. PIT-1 upregulation in breast tumors increases cell proliferation and the expression of two breast cancer-related hormones, growth hormone (GH) and prolactin (PRL), leading to MMPs upregulation and breast cancer metastasis. Human POU1F1 gene encodes two alternatively spliced isoforms, where Pit-1A (GHF-2) a.a. 47-73 is truncated to a single Thr47 residue in Pit-1B (GHF-1). Both PIT-1 isoforms contain a PIT-1 POU-specific domain (a.a. 150-224 of Pit-1A or a.a. 124-198 of Pit-1B) and a DNA-binding Homeobox (a.a. 240-299 of Pit-1A or a.a. 214-273 of Pit-1B).