Abstract
Cytosine methylation plays critical role in epigenetic regulation. Generally methylated cytosine represses the extension step in mRNA synthesis to suppress the gene expression.
We succeeded to induce RNAi that is targeted against spectinomycin resistance related aadA gene by introducing inverted repeat (IR) trnasgene in Chlamydomonas reinhardtii. However, without rearrangement of the target gene and the silencer, silencing intensity drifted severely through somatic cell divisions. After period, sub-clones originated in a particular transformant revealed various extent of silencing intensity. Comparative analysis of sub-clones showed that CG-methylation is heavily accumulated at IR region and the amount of the accumulated hairpin RNA is limited when the clone showed restrained RNAi. Moreover, accumulation of 3'-truncated immature IR transcripts was prominent in such transformants. While, target aadA gene is not methylated at all. Treatment by TSA enhanced accumulation of hairpin RNA. This indicates that CG-methylation collaborated with deacetylated histone repressed the transcription of the silencer.
