engleski

De novo DNA methylation and regulation of gene expression in Arabidopsis

DNA methylation is one of several epigenetic mechanisms used by cells to defend the genome against selfish DNA and to control gene expression. DNA methylation and demethylation control genome stability, responses to biotic and abiotic stresses and regulate develo pment. Promoter- methylated genes generally show tissue- specific expression and methylation within promoter regions commonly leads to lower gene expression. Plant DNA methylation occurs at CG, CHG and CHH (an asymmetric site, where H is A, C or T) sequences, each of which has different genetic requirements for the preservation. Nonsymmetrical CHH methylation cannot be sustained by the maintenance and require de novo methylation in each cell cycle through a process called RNA-directed DNA methylation (RdDM) . Two plant specific RNA polymerases, Pol IV and Pol V produce 24 –nucleotide small interfering RNAs and long non-coding RNAs respectively. In th is prosess the DDR complex is required for Pol V- chromatin interaction and transcription, while de novo methylase is targeted to specific locus by nascent Pol V transcript and methylate cytosine in C HH context. It is still not clear how DDR and Pol V are targeted to specific regions in the genome and to what extent RdDM regulate gene expression. Small family of BPM proteins from Arabidopsis has important role in plant flowering, seed development and abiotic stress responses. BPMs directly interact with different transc ription factors and target them for proteasomal degradation. Furthermore, in TAP tag experim ent we identified proteins from DDR complex as BPM1 interactors and suppose that DDR and Pol V could be recruited to promoters by BPMs and sequence specific transcription factors, as occurs with Pol II. The possible role of BPM proteins in navigating RdDM will be presented.

Arabidopsis thaliana ; DNA methylation ; DDR complex ; gene expression ; BPM

prezentirala N.Bauer