35S Promoter Methylation in Kanamycin-Resistant Kalanchoe (Kalanchoe pinnata L.) Plants Expressing the Antimicrobial Peptide Cecropin P1 Transgene

Transgenic kalanchoe plants (Kalanchoe pinnata L.) expressing the antimicrobial peptide cecropin P1 gene (cecP1) under the control of the 35S cauliflower mosaic virus 35S RNA promoter and the selective neomycin phosphotransferase II (nptII) gene under the control of the nopaline synthase gene promoter were studied. The 35S promoter methylation and the cecropin P1 biosynthesis levels were compared in plants growing on media with and without kanamycin. The low level of active 35S promoter methylation further decreases upon cultivation on kanamycin-containing medium, while cecropin P1 synthesis increases.

Expression of exogenous DNA methyltransferases: application in molecular and cell biology

DNA methyltransferases might be used as powerful tools for studies in molecular and cell biology due to their ability to recognize and modify nitrogen bases in specific sequences of the genome. Methylation of the eukaryotic genome using exogenous DNA methyltransferases appears to be a promising approach for studies on chromatin structure. Currently, the development of new methods for targeted methylation of specific genetic loci using DNA methyltransferases fused with DNA-binding proteins is especially interesting. In the present review, expression of exogenous DNA methyltransferase for purposes of in vivo analysis of the functional chromatin structure along with investigation of the functional role of DNA methylation in cell processes are discussed, as well as future prospects for application of DNA methyltransferases in epigenetic therapy and in plant selection.

Effect of hypermethylation of CCWGG sequences in DNA of Mesembryanthemum crystallinum plants on their adaptation to salt stress

Under salt stress conditions, the level of CpNpG-methylation (N is any nucleoside) of the nuclear genome of the facultative halophyte Mesembryanthemum crystallinum in the CCWGG sequences (W = A or T) increases two-fold and is coupled with hypermethylation of satellite DNA on switching-over of C3-photosynthesis to the crassulacean acid metabolism (CAM) pathway of carbon dioxide assimilation. The methylation pattern of the CCWGG sequences is not changed in both the 5'-promoter region of the gene of phosphoenolpyruvate carboxylase, the key enzyme of C4-photosynthesis and CAM, and in the nuclear ribosomal DNA. Thus, a specific CpNpG-hypermethylation of satellite DNA has been found under conditions of expression of a new metabolic program. The functional role of the CpNpG-hypermethylation of satellite DNA is probably associated with formation of a specialized chromatin structure simultaneously regulating expression of a large number of genes in the cells of M. crystallinum plants on their adaptation to salt stress and switching-over to CAM metabolism.

Hypermethylation of 5 -Region of the Human Calcitonin Gene in Leukemias: Structural Features and Diagnostic Significance

Methylation of the 5'-region of the calcitonin gene was investigated in bone marrow and peripheral blood cells of 27 healthy volunteers and 25 leukemic patients. In all patients suffering from various forms of myeloid and lymphoid leukemia, hypermethylation of CpG sequences was observed in this region of the calcitonin gene. Cytosine hypermethylation in the CpG sequence did not involve cytosines of adjacent CpNpG sequences (where N is any nucleoside). The 5'-region of the calcitonin gene lacked CpNpG methylation both in healthy controls and in leukemic patients; this apparently represents specific "non-alternative" type of CpG methylation in the extended DNA sequence. Methylation of the calcitonin gene was monitored in 18 leukemic patients during malignant progression and medical treatment. Hypermethylation of the calcitonin gene was not observed on long-term clinical hematological remission. In ten patients characterized by unstable (or incomplete) remission hypermethylation of the calcitonin gene persisted through the whole period of observation. In relapses, hypermethylation of the calcitonin gene appeared again and in six patients, this "molecular relapse" being registered 1-8 months before onset of clinical and laboratory signs of disease progression. The leukemia-specific hypermethylation of CpG sequences of the 5'-region of the calcitonin gene is a promising prognostic and diagnostic marker of leukemias and might be useful for monitoring of this disease.