1. Friedrich Miescher Institute, PO Box 2543, CH-4002 Basel, Switzerland
2. These authors contributed equally to this work.

Correspondence to: Yoshiki Habu¹ Correspondence and requests for materials should be addressed to Y. Habu (e-mail: Email: habu@fmi.ch). Accession numbers for the complete MOM genomic sequence (Co) and cDNA (Zh) are AF213628 and AF213627, respectively.

Abstract

Epigenetic modifications change transcription patterns in multicellular organisms to achieve tissue-specific gene expression and inactivate alien DNA such as transposons or transgenes^{1, 2}. In plants and animals, DNA methylation is involved in heritability and flexibility of epigenetic states³, although its function is far from clear. We have isolated an Arabidopsis gene, MOM, whose product is required for the maintenance of transcriptional gene silencing. Mutation of this gene or depletion of its transcript by expression of antisense RNA reactivates transcription from several previously silent, heavily methylated loci. Despite this, the dense methylation at these reactivated loci is maintained even after nine generations, indicating that transcriptional activity and methylation pattern are inherited independently. The predicted MOM gene product is a nuclear protein of 2,001 amino acids containing a region similar to part of the ATPase region of the SWI2/SNF2 family, members of which are involved in chromatin remodelling⁴. MOM is the first known molecular component that is essential for transcriptional gene silencing and does not affect methylation pattern. Thus, it may act downstream of methylation in epigenetic regulation, or be part of a new pathway that does not require methylation marks.

1. Friedrich Miescher Institute, PO Box 2543, CH-4002 Basel, Switzerland
2. These authors contributed equally to this work.

Correspondence to: Yoshiki Habu¹ Correspondence and requests for materials should be addressed to Y. Habu (e-mail: Email: habu@fmi.ch). Accession numbers for the complete MOM genomic sequence (Co) and cDNA (Zh) are AF213628 and AF213627, respectively.