Expression of telomerase catalytic subunit (hTERT) mRNA does not predict survival in patients with transitional cell carcinoma of the upper urinary tract.

Telomerase is a ribonucleoprotein enzyme that synthesizes telomeric repeats onto chromosomal ends using a segment of its RNA component as a template. Its activity has become an established indicator of the diagnosis, biological behavior, and prognosis of several tumors. However, few studies have investigated the diagnostic and prognostic importance of the expression of telomerase catalytic subunit (hTERT) mRNA in transitional cell carcinoma of the upper urinary tract (TCC-UUT). We investigated the expression of hTERT mRNA using in situ hybridization in 125 cases of TCC-UUT, and also its relation with the expression of telomerase RNA component (hTERC), proliferating cell nuclear antigen (PCNA) immunoreactivity, clinicopathologic parameters, and clinical outcome. A positive expression of hTERT mRNA was recognized in 93.6% of the samples and was apparent within the cytoplasm of tumor cells. In the normal urothelium examined in a few cases, its expression was barely detected. hTERT mRNA scores showed a significant association with hTERC score. However, no relationship was found between the expression of hTERT mRNA and clinicopathologic findings, PCNA index, or prognosis. These results suggest that the expression of hTERT mRNA does not predict prognosis in TCC-UUT.     

Telomerase catalytic subunit in laryngeal carcinogenesis--an immunohistochemical study.

We recently demonstrated that (1) telomerase catalytic subunit messenger RNA (mRNA) relative quantities increase progressively with the degree of laryngeal epithelial abnormalities and that (2) telomerase catalytic subunit gene re-expression represents an early event in laryngeal carcinogenesis. The aim of the study was to determine whether telomerase catalytic protein immunohistochemisty reflects telomerase catalytic subunit gene expression in different grades of laryngeal epithelial abnormalities and squamous cell carcinomas of the larynx. Telomerase catalytic protein was analysed immunohistochemically in 106 laryngeal epithelial tissue samples: 10 normal epithelia, 15 squamous cell hyperplasias, 14 basal/parabasal cell hyperplasias, 10 atypical hyperplasias, eight intraepithelial carcinomas and 49 squamous cell carcinomas. At least 200 nuclei of each lesion were quantified per slide and the number of positive signals per nucleus was expressed as a telomerase catalytic protein index. The mean telomerase catalytic protein index increased progressively with the degree of laryngeal epithelial abnormalities: from 0.17 in normal epithelia, 0.44 in squamous cell hyperplasia, 0.54 in basal/parabasal cell hyperplasia, 0.91 in atypical hyperplasia, 1.05 in intraepithelial carcinoma to 0.96 in squamous cell carcinomas. Statistical analysis revealed three different groups of laryngeal epithelial changes according to the number of telomerase catalytic protein signals per nucleus: (1) normal epithelium, (2) regenerative epithelium (squamous cell hyperplasia, basal/parabasal cell hyperplasia), and (3) atypical hyperplasia, intraepithelial carcinoma and squamous cell carcinoma (P<0.0033). Telomerase catalytic protein immunohistochemistry parallels well with telomerase catalytic subunit mRNA relative quantities in laryngeal carcinogenesis. In normal and regenerative laryngeal epithelia, telomerase catalytic protein is present in occasional basal/parabasal nuclei, becomes undetectable with maturation or differentiation of epithelial cells, and reflects the regenerative capacity of squamous epithelium. Nevertheless, several telomerase catalytic protein signals in the majority of nuclei in precancerous lesions, intraepithelial carcinomas and squamous cell carcinomas, are consistent with telomerase catalytic subunit gene re-expression, an early event in laryngeal carcinogenesis.     

In vitro translation of tobacco etch virus RNA

The wheat-embryo-derived cell-free system was optimized for translation of tobacco etch virus (TEV) RNA. When examined by polyacrylamide gel electrophoresis, the product of the TEV RNA stimulated system proved to be a single protein with a molecular weight of 40,000. This finding is different from results obtained when TEV RNA is used as a template in the rabbit reticulocyte lysate in vitro protein-synthesizing system.     

Template boundary definition in mammalian telomerase

Telomerase uses a short template sequence in its intrinsic RNA component to synthesize telomere repeats. Disruption of the helix P1b in human telomerase RNA or alteration of its distance from the template resulted in telomerase copying residues past the normal template boundary both in vivo and in vitro. Therefore, helix P1b is important for template boundary definition in human telomerase. Mouse telomerase RNA lacks helix P1b, and the boundary is established at 2 nt downstream of the 5'-end. The divergent structure of boundary definition elements in mammals, yeast, and ciliates suggests diverse mechanisms for template boundary definition in telomerase.     

Stimulation of Hepatitis C Virus RNA translation by microRNA-122 occurs under different conditions in vivo and in vitro

Translation of the Hepatitis C Virus (HCV) positive strand RNA genome is directed by an internal ribosome entry site (IRES) in the viral RNA's 5'-untranslated region (5'-UTR). HCV propagates preferentially in the liver, and HCV translation is stimulated by the liver-specific microRNA-122 (miR-122) acting on two target sites in the 5'-UTR. This stimulation is effective in living cells containing miR-122 and also in the rabbit reticulocyte lysate in vitro-translation system after addition of miR-122. Another RNA sequence located in the Core protein coding sequence can base-pair in a long-range RNA-RNA interaction to the HCV 5'-UTR, overlapping with the miR-122 target sites and the short spacer between them, and thereby inhibits HCV translation. Here we show genetic evidence that in reticulocyte lysate single-stranded miR-122 interferes with this inhibitory long-range RNA-RNA interaction and thereby contributes to enhanced HCV translation, involving not only the 5'-seed sequence of miR-122 but also sequences at its 3'-end. Also RNA oligonucleotides shorter than a typical microRNA stimulate HCV translation, confirming that in the reticulocyte lysate the stimulation of HCV translation functions by displacement of the inhibitory long-range interaction by miR-122. In contrast, in transfected HuH-7 hepatoma cells and in HeLa cells this interference of miR-122 with the inhibitory long-range RNA-RNA interaction plays not a major role, but only duplex miR-122 RNAs of the correct length stimulate HCV translation. These results suggest that: (1) the processing of the microRNA precursors and (2) the events occurring at the HCV RNA differ between cells and reticulocyte lysate.     

Identification of an initial site of interaction and possible helix destabilizing activity preceding initiation of protein synthesis from retrovirus RNA

Hybrid arrest of translation initiation (HARTI) assays with a series of oligodeoxyribonucleotides demonstrated that in rabbit reticulocyte lysate (RRL), the initial binding of protein synthesizing components to Rous sarcoma virus RNA requires only the penultimate guanosine and cap structure. Assays of DNA:RNA heteroduplex stability in RRL suggest that helix destabilizing activities then play a role in subsequent initiation of protein synthesis.     

端粒、端粒酶与肿瘤

瑞粒、端粒酶与肿瘤之间的密切关系提示攻克肿瘤的可能性,因此越来越引起人们的重视。本文就端粒、端粒酶与肿瘤的关系研究进展予以阐述。l端粒（Telomere）瑞拉是真核生物线形染色体3’末端一段重复DNA序列与结合蛋白的复合体l’］。在人类细胞中,这段重复DNA序列以（TTAGGG）n的形式存在,而在其他真核生物细胞,重复的端粒DNA单位的长度多为5到8个碱基对,亦富含鸟瞟吟（G）I’］。瑞拉结合蛋白是与端粒重复DNA序列结合的特异性蛋白。它能使端粒DNA避免被化学修饰和降解,还能参与瑞粒长度和瑞粒酶活性的调节［’］。瑞拉结…