Study on the correlation between telomere dysfunction of human gastric mucosa and chronic atrophic gastritis / 中华消化杂志

Objective:To investigate the correlation between telomere dysfunction of human gastric mucosa and chronic atrophic gastritis (CAG).Methods:From February 12, 2019 to July 10, 2020, at Endoscopy Center, Guang′anmen Hospital, China Academy of Chinese Sciences, 30 patients received endoscopy and pathological diagnosed with CAG (CAG group) were collected, and 30 patients with chronic non-atrophic gastritis (CNAG) were collected at the same time (CNAG group). The relative telomere length was detected by real time fluorescent quantitative polymerase chain reaction. The expression of telomere repeat binding factor (TRF) 1, TRF2 and protection of telomere (POT) 1 at protein level were detected by immunohistochemical staining and semi-quantitative analysis. Spearman analysis was used to analyze the correlation between the relative telomere length of gastric mucosa and the protein expression levels of TRF1, TRF2 and POT1. Mann-Whitney U test and independent sample t test were used for statistical analysis. Results:The relative telomere length of the gastric mucosa in the CAG group was shorter than that in the CNAG group (0.67 (0.51 to 1.17) vs. 1.06(0.69 to 1.37)), and the difference was statistically significant ( U=297.00, P=0.024). The protein expression levels of TRF1, TRF2, and POT1 in the CAG group were all higher than those in the CNAG group, respectively (4.26±2.49 vs. 1.86±1.34, 10.12±2.76 vs. 8.78±2.81, 4.22±2.48 vs. 2.53±1.62), and the differences were statistically significant ( t=8.05, 3.23, 5.39; P<0.001, =0.001, and <0.001). In the CAG group, the protein expression levels of TRF2 and POT1 in gastric mucosa were negatively correlated with the relative telomere length ( r=-0.477 and -0.417, P=0.008 and 0.022). Conclusions:The telomere dysfunction is related to the pathogenesis of CAG. The change of telomere binding protein expression level is involved in the shortening of telomere and pathological process of CAG patients.

Development and characterization of polyclonal antibodies against the linker region of the telomere-binding protein TRF2

Background: TRF2 (telomeric repeat binding factor 2) is an essential component of the telomere-binding protein complex shelterin. TRF2 induces the formation of a special structure of telomeric DNA and counteracts activation of DNA damage-response pathways telomeres. TRF2 has a poorly characterized linker region (udTRF2) between its homodimerization and DNA-binding domains. Some lines of evidence have shown that this region could be involved in TRF2 interaction with nuclear lamina. Results: In this study, the fragment of the TERF2 gene encoding udTRF2 domain of telomere-binding protein TRF2 was produced by PCR and cloned into the pET32a vector. The resulting plasmid pET32a-udTRF2 was used for the expression of the recombinant udTRF2 in E. coli RosettaBlue (DE3). The protein was isolated and purified using ammonium sulfate precipitation followed by ion-exchange chromatography. The purified recombinant protein udTRF2 was injected into guinea pigs to generate polyclonal antibodies. The ability of anti-udTRF2 antibodies to bind endogenous TRF2 in human skin fibroblasts was tested by western blotting and immunofluorescent staining. Conclusions: In this study, the recombinant protein udTRF2 and antibodies to it were generated. Both protein and antibodies will provide a useful tool for investigation of the functions of the udTRF2 domain and its role in the interaction between TRF2 and nuclear lamina.

The inhibition of hTERT and TRF2 gene expression and inducing cells apoptosis by adenovirus-mediated hTERT/TRF2 RNA interference in MCF-7 cells / 中国癌症杂志

Background and purpose: High expression of telomerase and telomere stability are two common features in tumor cell. hTERT is a catalytic subunit of telomerase, TRF2 is extremely important to maintain the length and stability of telomerase. This study was to construct the recombinant adenovirus mediated shRNA to hTERT and TRF2, and to investigate the inhibitory effects of the vector by solo-inhibiting and connect-inhibiting in the MCF-7 cells, in order to present a new approach to the gene therapy for breast cancer. Methods: rAd-hTERT and rAd-TRF2 were constructed and the expression of hTERT mRNA and TRF2 mRNA were tested by FQ-PCR 48 hours after transfecting in MCF-7 cells. Apoptosis was observed by flow cytometry 1 to 6 days after transfection. Results: ①At 48 hours after transfection, the results of FQ-PCR showed that compared to PBS group, the expression of hTERT in rAd-hTERT group was obviously decreased and the inhibition ratio was about 86%, but TRF2 had not been obviously inhibited (P>0.05);the expression of TRF2 in rAd-TRF2 group was obviously decreased and the inhibition ratio was about 80%, but hTERT had not been obviously inhibited (P>0.05);in rAd-hTERT/rAd-TRF2 group, the inhibition ratio of hTERT and TRF2 were about 88% and 85%. Comparing rAd-hTERT/rAd-TRF2 group with rAd-hTERT group and rAd-TRF2 group, there were no significant differences of inhibition ratio between hTERT gene and TRF2 gene(P>0.05). Otherwise, comparing rAd-HK group, rAd-blank group with PBS group, there were no significant differences of inhibition ratio between hTERT gene and TRF2 gene(P>0.05). ②The result of flow cytometry showed that apoptosis was induced at the first day after transfecting in rAd-hTERT group and rAd-TRF2 group, the most obvious apoptosis was in the 3rd to 5th days,at the peak in the 5th day, and decreased in the 6th day after transfection. The apoptosis ratio of rAd-hTERT group was 46.2%, rAd-TRF2 group was 43.5%. The apoptosis ratio of rAd-hTERT/rAd-TRF2 group was 46.2% at first day, 68.5% at the second day, the most obvious apoptosis was in the 3rd to 6th days and was 77.6% in the 6th days in rAd-hTERT/rAd-TRF2 group. There were significant differences in apoptosis ratio in solo-inhibiting and connect-inhibiting(P<0.05). In addition, comparing rAd-HK group, rAd-blank group with PBS group, there were no significant differences in apoptosis ratio(P>0.05). Conclusion: ①Target sequence of RNAi which aimed at hTERT gene and TRF2 gene was designed efficiently, and the RNAi expression vectors were seen in vivo study efficiently and specifically inhibited the correspond gene expression and promoted cell apoptosis in MCF-7 cells. ②rAd-hTERT vector and rAd-TRF2 vector have no synergistical effect and antagoinstical effect on inhibiting hTERT gene and TRF2 gene mRNA expressing in MCF-7, but there was synergistical effect in terms of the induction of apoptosis. So association-RNAi-technique targeting to the genes of telomere length and stability can effectively promote tumor cell into apoptosis and inhibit breast cancer cell growth. RNAi technique of connecting correlation genes is a more effective gene therapy strategy.