Securin
cytosol
hpttg, a human homologue of rat pttg, is overexpressed in hematopoietic neoplasms. Evidence for a transcriptional activation function of hPTTG.
We have isolated a human cDNA clone encoding a novel protein of 22 kDa that is a human counterpart of the rat oncoprotein PTTG. We show that the corresponding gene (hpttg) is overexpressed in Jurkat cells (a human T lymphoma cell line) and in samples from patients with different kinds of hematopoietic malignancies. Analysis of the sequence showed that hPTTG has an amino-terminal basic domain and a carboxyl-terminal acidic domain, and that it is a proline-rich protein with several putative SH3-binding sites. Subcellular fractionation studies show that, although hPTTG is mainly a cytosolic protein, it is partially localized in the nucleus. In addition we demonstrate that the acidic carboxyl-terminal region of hPTTG acts as a transactivation domain when fused to a heterologous DNA binding domain, both in yeast and in mammalian cells.