Hepatoma Up-regulated Protein Research Articles

Enhanced transformation and chemosensitivity of NIH3T3 cells transduced with hepatoma up-regulated protein

Hepatoma up-regulated protein (HURP) is a recently identified novel cell-cycle-regulated gene. The HURP gene is overexpressed in human hepatocellular carcinoma and transitional cell carcinoma. The cellular function of HURP is not fully understood. In this study, the NIH3T3 cells transduced with the exogenous HURP gene manifested the general characteristics of tumor cells, which had higher growth rate in low-serum media and advanced ability of colony formation on agarose-based plates. Transduced HURP was capable of specifically enhancing the chemosensitivity of deoxycytosine analogs, such as gemcitabine, ARA-C, and 5-AZA-CdR, but neither had an effect on the response of DNA intercalating agents, such as cisplatin, carboplatin, and doxorubicin, nor on the response of microtubule stabilizers, such as paclitaxel, docetaxel, and vinblastine. These results indicate that the HURP gene might be a potential oncogenic gene and capable of enhancing the chemosensitivity of deoxycytosine analogs in NIH3T3 cells.

Fbx7 Functions in the SCF Complex Regulating Cdk1-Cyclin B-phosphorylated Hepatoma Up-regulated Protein (HURP) Proteolysis by a Proline-rich Region

F-box proteins, components of SCF ubiquitin-ligase complexes, are believed to be responsible for substrate recognition and recruitment in SCF-mediated proteolysis. F-box proteins that have been identified to function in the SCF complexes to date mostly have substrate-binding motifs, such as WD repeats or leucine-rich repeats in their C termini. However, many F-box proteins lack recognizable substrate-binding modules; whether they can function in the SCF complexes remains unclear. We show here that Fbx7, an F-box protein without WD repeats and leucine-rich repeats, is required for the proteasome-mediated proteolysis of the hepatoma up-regulated protein (HURP). Depletion of Fbx7 by small interfering RNA leads to depression of HURP ubiquitination and accumulation of HURP abundance. In the SCF(Fbx7) complex, Fbx7 recruits HURP through its C-terminal proline-rich region in a Cdk1-cyclin B-phosphorylation dependent manner. Mutation of the multiple Cdk1-cyclin B phosphorylation sites on HURP or the proline-rich region of Fbx7 abolishes the association between Fbx7 and HURP. Thus, Fbx7 is a functional adaptor of the SCF complex with a proline-rich region as the substrate-binding module. In addition to Fbx7, data base analyses reveal two putative mammalian proline-rich region-containing F-box proteins, KIAA1783 and RIKEN cDNA 2410015K21. Taken together, these findings further expound the diverse substrate-recognition abilities of the SCF complexes.

Identification of a novel cell cycle regulated gene, HURP, overexpressed in human hepatocellular carcinoma.

An analytic strategy was followed to identify putative regulatory genes during the development of human hepatocellular carcinoma (HCC). This strategy employed a bioinformatics analysis that used a database search to identify genes, which are differentially expressed in human HCC and are also under cell cycle regulation. A novel cell cycle regulated gene (HURP) that is overexpressed in HCC was identified. Full-length cDNAs encoding the human and mouse HURP genes were isolated. They share 72 and 61% identity at the nucleotide level and amino-acid level, respectively. Endogenous levels of HURP mRNA were found to be tightly regulated during cell cycle progression as illustrated by its elevated expression in the G(2)/M phase of synchronized HeLa cells and in regenerating mouse liver after partial hepatectomy. Immunofluorescence studies revealed that hepatoma up-regulated protein (HURP) localizes to the spindle poles during mitosis. Overexpression of HURP in 293T cells resulted in an enhanced cell growth at low serum levels and at polyhema-based, anchorage-independent growth assay. Taken together, these results strongly suggest that HURP is a potential novel cell cycle regulator that may play a role in the carcinogenesis of human cancer cells.

Potential molecular marker for detecting transitional cell carcinoma

Objectives. To assess the expression rate of a cancer-related gene, hepatoma-up-regulated protein (HURP), in the tumor tissue of transitional cell carcinoma (TCC), and to assess the potential suitability of using this gene as a novel molecular marker for detecting TCC in voided urine. Methods. Total RNA was extracted from 80 TCC tissue samples of the urinary tract. Forty-five of the 80 tumor-adjacent tissue samples were from the same patients and 15 were from control subjects (patients with benign prostatic hyperplasia). The expression levels of HURP mRNA in these specimens were examined using reverse transcriptase-polymerase chain reaction. The HURP mRNA transcripts in voided urine pellets from 14 additional patients were determined using the same method. The messages were normalized to beta-actin mRNA. Results. The detection of HURP expression in the TCC tissue samples had a sensitivity of 88.8% (71 of 80) and a specificity of 100% (15 of 15). Ten of the 45 grossly tumor-adjacent tissue samples expressed HURP mRNA, which may indicate subtle genetic changes in tissue adjacent to tumor. All seven urine specimens from the patients with TCC revealed HURP expression; however, no specimens from patients with nonmalignant diseases did so. Conclusions. A potential molecular marker for detecting TCC with tissue specimens and voided urine samples has been found. Although the real clinical application of this marker requires additional evaluation, the high sensitivity and specificity of the HURP gene amplification method warrants more investigation in the future.