engleski

Epigenetic signatures of chromatin in oak cycling cells

DNA methylation and covalent modifications of histones play an important role in chromatin dynamics and regulation of gene transcription. Cytosine methylation and methylation of histones H3 and H4 at lysine positions 9 and 20 (H3K9me and H4K20me) are marks for repressive, transcriptionally silent, chromatin (heterochromatin). Methylation of histone H3 at lysine 4 (H3K4me2) along with acetylaton of histone H3 at lysine 9 (H3K9ac) characterizes permissive chromatin state which is transcriptionally active (euchromatin). In this study we analysed the distribution of the epigenetic marks characteristic for repressive and permissive chromatin state in cycling cells of root-tips and in metaphase chromosomes of the common oak (Quercus robur). Immunodetection with antibodies against methylated histones H3 (H3K9me, H3K4me2) and acetylated histones H3 (H3K9ac) in interphase nuclei revealed a rather homogenous distribution of both euchromatic and heterochromatic histone marks. Signals corresponding to H3K4me2 and H3K9ac marks were found dispersed throughout the nucleus and only a few randomly distributed foci were observed. H3K9ac mark was absent from the nucleolus, suggesting lack of H3K9 acetylation in rRNA genes which predominantly constitute nucleolar chromatin. Even though H3K9me signals intensely stained the whole nucleus, this heterochromatic epigenetic mark sharply colocalized with chromocenters. Immunodetection of 5-methycytosine (5-mC) in revealed a homogenous spotty pattern throughout the entire interphase nuclei. Signals corresponding to H3K9ac mark and 5-mC were also homogenously distributed on the entire length of all oak chromosomes.

chromatin; epigenetic modifications; meristematic cells

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