Editors' ChoiceTranscriptonal Regulation

Mom Always Said "Silence is Golden"

Science's STKE  16 May 2000:
Vol. 2000, Issue 32, pp. tw4
DOI: 10.1126/stke.2000.32.tw4

The process of epigenesis allows organisms to control the expression of their genes in a tissue-specific or developmentally regulated manner. DNA methylation is involved in some forms of transcriptional control, such as silencing, but its function is not completely clear. Amedeo et al. have isolated a gene from Arabidopsis thaliana, termed MOM, that is essential for maintaining transcriptional silence. The authors demonstrate that genes that were previously silent are now activated in MOM mutants; however, the pattern of genomic DNA methylation remains the same when compared with that of wild-type plants. Mom protein localizes to the nucleus and shares regional sequence similarity with ATPases and DNA helicases, although this catalytic function has yet to be demonstrated for Mom. Indeed, helicases have two domains that work partially independently of each other; however, Mom has only the second of these domains. Therefore, the authors speculate that Mom may bind to another protein that has the first helicase domain, so as to maintain transcriptional silence. As compared to the stunted growth of mutant plants unable to properly methylate their DNA, MOM mutants grow properly and do not exhibit developmental abnormalities, suggesting that Mom may influence trancriptional control in a methylation-independent manner.

Amedeo, P., Habu, Y., Afsar, K., Scheid, O.M., and Paszkowski, J. (2000) Disruption of the plant gene MOM releases transcriptional silencing of methylated genes. Nature 405: 203-206. [Online Journal]