In Arabidopsis, an RNA-directed DNA methylation pathway （RdDM） is responsible for de novo establish- ment of DNA methylation and contributes to transcriptional gene silencing. Recently, the microrchidia （MORC）-typ...In Arabidopsis, an RNA-directed DNA methylation pathway （RdDM） is responsible for de novo establish- ment of DNA methylation and contributes to transcriptional gene silencing. Recently, the microrchidia （MORC）-type ATPases were shown to play essential roles in enforcing transcriptional gene silencing of a subset of genes and transposons by regulating the formation of higher-order chromatin architecture. How- ever, how MORC proteins cooperate with the RdDM pathway components to regulate gene expression re- mains largely unclear. In this study, SUVH9 and MORC6 were identified from a screening of suppressors of idml, which is a mutant defective in active DNA demethylation. SUVH9 and MORC6 are required for silencing of two reporter genes and some endogenous genes without enhancing DNA methylation levels. SUVH9, one of SU（VAR）3-9 homologs involved in RdDM, directly interacts with MORC6 and its two close homologs, MORC1 and MORC2. Similar to MORC6, SUVH9 and its homolog SUVH2 are required for hetero- chromatin condensation and formation of 3D chromatin architecture at SDC, and Solo-LTR loci. We propose that SUVH2 and SUVH9 bind to the methylated DNA and facilitate the recruitment of a chromatin- remodeling complex to the target loci in association with MORC proteins.展开更多
文摘In Arabidopsis, an RNA-directed DNA methylation pathway （RdDM） is responsible for de novo establish- ment of DNA methylation and contributes to transcriptional gene silencing. Recently, the microrchidia （MORC）-type ATPases were shown to play essential roles in enforcing transcriptional gene silencing of a subset of genes and transposons by regulating the formation of higher-order chromatin architecture. How- ever, how MORC proteins cooperate with the RdDM pathway components to regulate gene expression re- mains largely unclear. In this study, SUVH9 and MORC6 were identified from a screening of suppressors of idml, which is a mutant defective in active DNA demethylation. SUVH9 and MORC6 are required for silencing of two reporter genes and some endogenous genes without enhancing DNA methylation levels. SUVH9, one of SU（VAR）3-9 homologs involved in RdDM, directly interacts with MORC6 and its two close homologs, MORC1 and MORC2. Similar to MORC6, SUVH9 and its homolog SUVH2 are required for hetero- chromatin condensation and formation of 3D chromatin architecture at SDC, and Solo-LTR loci. We propose that SUVH2 and SUVH9 bind to the methylated DNA and facilitate the recruitment of a chromatin- remodeling complex to the target loci in association with MORC proteins.
