Fig. 6

A feed-forward model illustrating the regulation of Evelknievel (EK) retroelement by CMT3 and CMT1 proteins. a Silencing of EK inserted within the CMT1 gene. CMT3 in concert with SUVH4/KYP maintain cytosine methylation over the entire EK and 3′ CMT1 region, particularly at the CHG and CHH contexts (red and green lollipops, respectively) and to some extent also CG methylation (blue lollipops) as well as histone methylation at lysine 9, resulting in a complete silencing of EK. Consequently, transcription from the CMT1 promoter proceeds through the EK to the CMT1 transcription termination site. The CMT1/EK/CMT1 transcript undergoes splicing in which EK is spliced out faithfully (in 25% of the events), leading to reformation of mature CMT1 mRNA and possibly to retrieval of a functional CMT1 protein, which could potentially further methylates EK to ensure its own expression. b Activation of EK. In the absence of KYP or CMT3, EK is transcriptionally activated due to absence of CHH and CHG methylation, resulting in transcriptional interference of CMT1 rendering it incapable of transcription beyond the EK insertion site. This leads to formation of a truncated CMT1 mRNA and to an aberrant, non-functional CMT1 protein