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MicroRNAs are small noncoding RNAs that regulate gene expression; stabilize the cell phenotype; and play an important role in cell differentiation, development, and apoptosis. A canonical microRNA biogenesis pathway includes several posttranscriptional steps of processing and transport and ends with cytoplasmic cleavage of pre-miRNA by type III ribonuclease DICER to form a mature duplex, which is included in RISC. MicroRNA biogenesis and role in cell stress are still poorly understood. Using flow cytometry and high-throughput analysis of gene expression, we have shown that chronic endoplasmic reticulum (ER) stress, which is associated with improper protein folding in the ER, induce a cellular senescence phenotype in fibroblast-like FRSN cells. While acute ER stress can reduce miRNA biogenesis, chronic stress does not cause a significant drop in global microRNA expression and is accompanied by only a slight decrease in DICER1 mRNA expression. Heterogeneity with respect to lysosomal β-galactosidase activity was found to increase in the cell population exposed to ER stress. We do not exclude induced cell heterogeneity regarding expression of components of the microRNA biogenesis pathway.

Universal Russian reagents for real time PCR were tested and compared with reference reagents provided by foreign companies. Testing was carried out on plasmids with cloning fragments (DNA-standards) of cDNA with chimeric (fusion) gene PML-RARalpha. Values of amplification efficiency of Russian and foreign reagents were measured on samples with serial dilutions (30-300000 copies) of cloned cDNA fragments of PML-RARalpha and internal control gene ABL. Amplification efficiencies of Russian and foreign reagents were found to be close one to another. Russian universal reagent kit RealityTM and ABI TaqMan Core Reagent Kit have amplification efficiencies 1.919 and 1.929, and correlation coefficients of copy numbers PML-RARalpha0.999 and 0.996, respectively. These values were determined by construction of a standard curve. To verify these results we studied also the samples of cDNA from blood and bone marrow of patients with acute promyelocytic leukemia. All samples posses translocation t(15;17), and appropriate chimeric gene PML-RARalpha. copy number in 1 microg of total RNA was in range 5.86 x 10(4)-8.315 x 10(5) before chemotherapy. No symptoms of minimal residual disease were found after 3.5 months since chemotherapy - fusion gene PML-RARalpha was not detected by real time PCR method. These results are in agreement with clinical data. Our investigations tend to show that application of RealityTM reagent set in real timePCR experiments gives correct results and may be used in molecular oncodiagnostics.