The role of HuR in the post-transcriptional regulation of interleukin-3 in T cells.

Human Interleukin-3 (IL-3) is a lymphokine member of a class of transiently expressed mRNAs harboring Adenosine/Uridine-Rich Elements (ARE) in their 3' untranslated regions (3'-UTRs). The regulatory effects of AREs are often mediated by specific ARE-binding proteins (ARE-BPs). In this report, we show that the human IL-3 3'-UTR plays a post-transcriptional regulation role in two human transformed cell lines. More specifically, we demonstrate that the hIL-3 3'-UTR represses the translation of a luciferase reporter both in HeLa and Jurkat T-cells. These results also revealed that the hIL-3 3'-UTR-mediated translational repression is exerted by an 83 nt region comprised mainly by AREs and some non-ARE sequences. Moreover, electrophoretic mobility shift assays (EMSAs) and UV-crosslinking analysis show that this hIL-3 ARE-rich region recruits five specific protein complexes, including the ARE-BPs HuR and TIA-1. HuR binding to this ARE-rich region appears to be spatially modulated during T-cell activation. Together, these results suggest that HuR recognizes the ARE-rich region and plays a role in the IL-3 3'-UTR-mediated post-transcriptional control in T-cells.

Prognostic value of the expression of tumor suppressor genes p53, p21, p16 and prb, and Ki-67 labelling in high grade astrocytomas treated with radiotherapy.

Cumulative inactivation of tumor suppressor genes and/or amplification of oncogenes lead to progressively more malignant astrocytic tumors. We have analyzed the significance of tumor suppressor genes p53, p21, p16 and retinoblastoma protein (pRb) and proliferative activity for survival in 77 high grade astrocytic tumors. After operation, the patients--25 anaplastic astrocytomas (AA) and 52 glioblastomas (GBs)--were treated with similar radiotherapy. The expression of the suppressor genes and the proliferative activity were analyzed immunohistochemically. p53 immunopositivity was found in 44% of AAs and 46% of GBs. Tumors with aberrant p53 expression had lower proliferation indices than p53 immunonegative tumors. Neither p53 expression nor p21 immunonegativity (52% of AAs and 48% of GBs) correlated with survival. p16 immunostaining was negative in 16% of AAs and in 44% of GBs, and it correlated inversely with survival in both uni- and multivariate analyses. pRb immunostaining was negative only in 8% of both AAs and GBs and the absence of p16 and pRb were mutually exclusive. Ki-67 labelling index (LI) was significantly higher in GBs (26.8%) than in AAs (20.3%), and in multivariate analysis it was an independent prognostic factor for survival. In 48% of AAs Ki-67 LI exceeded 20% and this subset of AAs had similar prognosis as GB. In high grade astrocytic tumors p16 immunonegativity was an independent indicator of poor prognosis in addition to the previously established patient's age, histopathology and Ki-67 LI. Furthermore, there was a subset of AAs with a high proliferation rate (> 20%) in which the histopathological hallmarks of GB were lacking, but which had similarly dismal prognosis as GB.