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Ricin A-chain ( RTA) depurinates the sarcin-ricin loop of 28S ribosomal RNA and inhibits protein synthesis in mammalian cells. In yeast, the ribosomal stalk facilitates the interaction of RTA with the ribosome and subsequent depurination. Despite homology between the stalk structures from yeast and humans, there are notable differences. The human ribosomal stalk contains two identical heterodimers of P1 and P2 bound to P0, whereas the yeast stalk consists of two different heterodimers, P1α- P2β and P2α- P1β, bound to P0. RTA exhibits higher activity towards mammalian ribosomes than towards ribosomes from other organisms, suggesting that the mode of interaction with ribosomes may vary. Here, we examined whether the human ribosomal stalk proteins facilitate the interaction of RTA with human ribosomes and subsequent depurination of the sarcin-ricin loop. Using small interfering RNA-mediated knockdown of P1/ P2 expression in human cells, we demonstrated that the depurination activity of RTA is lower when P1 and P2 levels are reduced. Biacore analysis showed that ribosomes from P1/ P2-depleted cells have a reduced ability to bind RTA, which correlates with reduced depurination activity both in vitro and inside cells. RTA interacts directly with recombinant human P1- P2 dimer, further demonstrating the importance of human P1 and P2 in enabling RTA to bind and depurinate human ribosomes. Structured digital abstract P2, P1 and RTA physically interact by surface plasmon resonance (View interaction), P2, P1 and RTA physically interact by anti bait coimmunoprecipitation (View interaction) [ABSTRACT FROM AUTHOR]

Abstract: The Aldo Keto Reductases (AKRs) are a superfamily of enzymes that catalyze the reduction of biogenic and xenobiotic aldehydes and ketones. AKR1B family has 2 known members in humans and 3 in rodents. Two novel gene loci, hereafter referred to as AKR1B15 in human and Akr1b16 in mouse have been predicted to exist within the AKR1B clusters. AKR1B15 displays 91% and 67% sequence identity with human genes AKR1B10 and AKR1B1, respectively while Akr1b16 shares 82–84% identity with murine Akr1b8 and Akr1b7. We tested the hypothesis that AKR1B15 and Akr1b16 genes are expressed as functional proteins in human and murine tissues, respectively. Using whole tissue mRNA, we were able to clone the full-length open reading frames for AKR1B15 from human eye and testes, and Akr1b16 from murine spleen, demonstrating that these genes are transcriptionally active. The corresponding cDNAs were cloned into pET28a and pIRES-hrGFP-1α vectors for bacterial and mammalian expression, respectively. Both genes were expressed as 36kDa proteins found in the insoluble fraction of bacterial cell lysate. These proteins, expressed in bacteria showed no enzymatic activity. However, lysates from COS-7 cells transfected with AKR1B15 showed a 4.8-fold (with p-nitrobenzaldehyde) and 3.3-fold (with dl-glyceraldehyde) increase in enzyme activity compared with untransfected COS-7 cells. The Akr1b16 transcript was shown to be ubiquitously expressed in murine tissues. Highest levels of transcript were found in heart, spleen, and lung. From these observations we conclude that the predicted AKR1B15 and 1b16 genes are expressed in several murine and human tissues. Further studies are required to elucidate their physiological roles. [Copyright &y& Elsevier]

Epidemiological studies have demonstrated that type 2 diabetes mellitus (T2DM) and hyperinsulinemia are associated closely with endometrial carcinoma risk, although the molecular mechanism remains unclear. Insulin receptor isoformA expression is upregulated in many cancer cells and tissues, which suggests that IR-A-mediated signaling pathways may have important implications for cancer pathogenesis. We measured the expression of insulin receptor isoforms (IR-A and IR–B in the normal endometrium tissues, the endometrial carcinoma tissues and the endometrial carcinoma cell lines. We found that the total insulin receptor (IR) and IR-A expression mRNA levels and the ratio of IR-A to total IR in endometrial carcinoma specimens were significantly higher than them in control endometrial tissue specimens(P<0.05). Further analysis indicated that the tendency was more prominently in patients with T2DM. IR-A mRNA was differentially expressed in four endometrial carcinoma cell lines (Ishikawa, KLE, RL95-2 and HEC-1-A. RL95-2 cells have a low endogenous IR-A expression, and these were used to construct a stable cell line overexpressing IR-A. We found that IR-A overexpression significantly increased cell proliferation, the proportion of cells in S phase, activation of the Akt pathway and tumorigenicity of xenografts in nude mice. In contrast, there was no significant difference in the the percentage of apoptotic cells between cells overexpressing IR-A and control cells. Moreover, levels of phosphorylated ERK1/2 protein were significantly decreased in cells overexpressing IR-A relative to controls. These findings reveal the pivotal role of IR-A in endometrial cancer carcinogenesis, and suggest that the association of elevated IR-A levels with cell proliferation and tumorigenicity may be causally linked to its effect on the proportion of cells in S phase and the activation of the Akt pathway. [ABSTRACT FROM AUTHOR]

• The full length of Rhododendron micranthum Turcz. RmCS was isolated and identified. • RmCS was preferentially expressed in stem, autumn leaf and initial flowering stage. • Overexpression of RmCS increased salt tolerance, alkali tolerance, drought tolerance and aluminum tolerance of transgenic tobacco, but decreased plant height and leaf area. • The roots of tobacco plants overexpressing RmCS secreted higher concentrations of malic acid, citric acid and tartaric acid. Citrate synthase (CS) is a rate-limiting enzyme in tricarboxylic acid (TCA) cycle, which is related to numerous plant physiological events, like mitochondrial energy metabolism and stress resistance, and has a key function in aluminum (Al) stress response. Rhododendron micranthum Turcz. has been used as ornamental plants worldwide. This species prefers acidic soils, and thus its growth and ornamental quality are often limited by Al toxicity. In the present work, the full-length cDNA encoding a CS (here designated RmCS) was isolated and characterized. The RmCS contained the conserved CS domain and a N-terminal PWPN-box. RmCS protein was predicted to be localized to the cytoplasm and mitochondria. A neighbor-joining tree indicated that RmCS was similar to CS proteins of Actinidia chinensis var. chinensis and Vitis riparia the most. RmCS was highly expressed in stems; particularly, it shows predominant expression in flowers in the first flowering period, whereas in leaves peak expression levels were detected in September. Southern blotting analysis demonstrated that one to three copies of RmCS were successfully integrated in the genome of transgenic tobacco. Overexpression of RmCS significantly increased salt, alkali, drought, and Al tolerance, but reduced the plant height and leaf area, of transgenic tobacco. Roots of RmCS -overexpressing tobacco plants secreted higher concentrations of malic acid, citric acid, and tartaric acid. Decreased malonaldehyde while elevated proline contents in the leaf suggested that the improved abiotic stress tolerance conferred by RmCS was associated with decreased membrane damage and improved osmotic adjustment. The above findings indicated the potentially vital function of RmCS in abiotic stress responses of R. micranthum , and lays certain theoretical foundation for improving stress resistance of R. micranthum. [ABSTRACT FROM AUTHOR]

Hepatic growth factor (HGF) has been widely used in studies on arterial remodeling after injury, and results turn out to be inconsistent. The changes of endogenous HGF expression after injury also remain controversial. This study clarified the role of exogenous human HGF (hHGF) gene transfer in neointimal hyperplasia and investigated the associated alterations of endogenous HGF and c-Met expressions under endothelial denudation with or without hHGF gene transfer using a balloon-injured rabbit aorta model. Sixty-one rabbits were randomly divided into normal controls, endothelial injury, endothelial injury with hHGF, or the control vector gene transfer groups. On weeks 1, 2, 4, and 8 after injury, neointimal hyperplasia and endothelialization were evaluated by the ratio of neointimal area to medial area (N/M ratio), CD31-positive staining, α-smooth muscle actin, and endothelial nitric oxide synthase expressions using histological analysis, immunohistochemistry staining, or real-time quantitative reverse transcriptase polymerase chain reaction. Endogenous rabbit HGF (rHGF) and c-Met expressions were detected with immunohistochemistry staining and quantitative reverse transcriptase polymerase chain reaction. It was found that expressions of endogeneous rHGF and c-Met in endothelial injury upregulated with peak levels on week 2 or week 4 after injury ( p  < 0.01). On week 1 after hHGF transfer, neointimal hyperplasia was significantly inhibited ( p  < 0.001), with decreased α-smooth muscle actin expression ( p  < 0.05) and improved endothelial cells regeneration and function ( p  < 0.01). More remarkable overexpression of endogenous rHGF and c-Met mRNAs were detected, and lowered positive staining of rHGF and c-Met was shown in the neointima ( p  < 0.05). These results demonstrated hHGF gene transfer induced further overexpression of endogenous rHGF and c-Met mRNAs but lowered immunoreactivities of rHGF and c-Met in the neointima, thus leading to significant attenuation of neointimal hyperplasia. [ABSTRACT FROM AUTHOR]

Abstract: Objective: The human papillomavirus (HPV) oncoprotein, E6, activates telomerase reverse transcriptase (TERT) expression and causes cellular immortalization. It remains unclear whether E6 affects TERT transcription by altering DNA methylation profiles. In this study, we explored the methylation status of the TERT promoter in cervical cancer cell lines and its variations after E6 was silenced by RNAi. Methods: Three kinds of cervical cell lines (HPV16 positive: CaSki and SiHa; HPV18 positive: HeLa), were taken to analyze the methylation status of the TERT promoter by methylation-specific polymerase chain reaction (MSP) and bisulfite sequencing (BS). Stealth RNAi was transiently transfected to these cell lines to silence the expression of HPV16/18 E6, and the subsequent changes of TERT mRNA levels and TERT promoter DNA methylation were examined. Results: Hypomethylation of the DNA around the TERT transcription start site (−156 to +162bp) was functionally related to its transcription. After transfection with Stealth RNAi, the levels of HPV16/18 E6 and TERT mRNA were greatly decreased. The methylated CpG around the transcription start sites in CaSki and SiHa cells were statistically increased (respectively P =0.016, P =0.000). However, there was no significant difference in HeLa cells (P =0.128). Conclusion: Hypomethylated CpG around the transcription start site enables the expression of TERT in cervical cancer cells. Our results show for the first time that HPV16 E6 can promote TERT transcription through demethylating the DNA sequence around the TERT transcription start site in cervical squamous cancer cells. [Copyright &y& Elsevier]