| Description | Identified through its interaction with pituitary tumor transforming 1 (PTTG), the PTTG1IP protein is 180 amino acids long with a molecular mass of approximately 25 kDa.
A putative signal peptide exists at the N-terminus (1-32). A domain of unknown function common to plexins, semaphorins and integrins (PSI) is located between residues 39-92. Adjacent to this is a putative transmembrane domain (95-122). A bipartite nuclear localisation signal (NLS) is located between amino acids 149 and 166. The C-terminal 30 amino acids of PTTG1IP contain the PTTG binding domain and a putative tyrosine-based sorting signal.
Potential post-translational modifications include putative phosphorlyation sites for cAMP- and cGMP-dependent kinase, protein kinase C and casein kinase II and five glycosylation sites for N-linked and O-linked oligosaccharides. |
| Expression | PTTG1IP is widely expressed and has been identified in all tissues examined including spleen, thymus, prostate, testis, ovary, small intestine, colon, leukocytes, spinal cord, thyroid, pituitary, lymph node, trachea, adrenal gland and bone marrow. |
| Localisation | A tagged PTTG1IP protein was located predominantly in the nucleus with partial expression also in the cytoplasm. Mutation of the NLS shifted PTTG1IP expression to a perinuclear and cytoplasm location. Other reports suggest that PTTG1IP is located predominantly in the cytoplasm. |
| Function | PTTG expression is predominantly nuclear in the presence of PTTG1IP. However, in the absence of PTTG1IP or with the NLS mutant of PTTG1IP, PTTG is mainly cytoplasmic. Hence, PTTG1IP is thought to facilitate the translocation of PTTG into the nucleus.
Itself upregulated by PTTG, PTTG1IP is required for the ability of PTTG to transactivate basic fibroblast growth factor (FGF2).
PTTG1IP has a described role in repressing iodide uptake into thyroid cells via transcriptional regulation of the sodium iodide symporter.
In MC3T3-El cells, PTTG1IP is regulated by the transcription factor Runx2, implying a role in osteoblast differentiation. |
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