hpttg, a human homologue of rat pttg, is overexpressed in hematopoietic neoplasms. Evidence for a transcriptional activation function of hPTTG

Abstract

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 di erent kinds of hematopoietic malignancies. Analysis of the sequence showed that hPTTG has an aminoterminal 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.

Cell cycle regulated expression and phosphorylation of hpttg proto-oncogene product

“…This hypothesis arose from the observation that hpttg is expressed at high levels, not only in tumor cells but also in normal tissues that contain proliferating cells (DomõÂ nguez et al, 1998;Zhang et al, 1999b).…”

“…One important feature found in the hPTTG sequence is the presence of short stretches of prolines that are putative binding sites for SH3 domains in other proteins (DomõÂ nguez et al, 1998). Mutation of prolines 163, 170, 172 and 173 abrogated the hPTTG in vitro transforming and in vivo tumor-inducing activity as well as stimulation of basic ®broblast growth factor, suggesting that hPTTG may function through SH3-mediated signal transduction pathways (Zhang et al, 1999b).…”

“…Anti-hPTTG polyclonal antibody was produced as described (DomõÂ nguez et al, 1998). Monoclonal anti-Cdc2 was from Transduction Labs.…”

“…Human pttg is expressed in pituitary adenomas and breast and lung tumors (Zhang et al, 1999a;Sa ez et al, 1999). A ®rst indication of the potential function of hPTTG was our demonstration that the acidic carboxyl-terminal region of hPTTG acts as a transactivation domain when fused to a heterologous DNA binding domain (Domõ nguez et al, 1998). More recently, the transforming activity of human pttg has been shown in NIH3T3 cells: stable transfection of these cells with hpttg cDNA caused anchorageindependent transformation in vitro and induced in vivo tumor formation when transfectants were injected into athymic mice (Zhang et al, 1999b).…”

hpttg is over-expressed in pituitary adenomas and other primary epithelial neoplasias

“…Transformation in vitro of 3T3 ®broblasts induced by pttg overexpression and tumor formation in athymic nude mice after injection of transfected cells suggest a role for this gene in pituitary tumorigenesis (Pei and Melmed, 1997). In our laboratory, a human cDNA homologue of pttg, hpttg, has been previously cloned from a human thymus cDNA library (DomõÂ nguez et al, 1998). To investigate the role of hpttg in human pituitary tumorigenesis, we examined its expression in normal human pituitary gland and di erent types of hormonesecreting and nonfunctioning human pituitary adenomas.…”