       Document 0708
 DOCN  M9630708
 TI    The reduced expression of endogenous duplications (REED) in the maize R
       gene family is mediated by DNA methylation.
 DT    9603
 AU    Ronchi A; Petroni K; Tonelli C; Dipartimento di Genetica e di Biologia
       dei microrganismi, Milano,; Italy.
 SO    EMBO J. 1995 Nov 1;14(21):5318-28. Unique Identifier : AIDSLINE
       MED/96080167
 AB    The duplicated R and Sn genes regulate the maize anthocyanin
       biosynthetic pathway and encode tissue-specific products that are
       homologous to helix-loop-helix transcriptional activators. As a
       consequence of their coupling in the genome, Sn is partially silenced.
       Genomic restriction analysis failed to reveal gross structural DNA
       alterations between the strong original phenotype and the weak
       derivatives. However, the differences in pigmentation were inversely
       correlated with differences in the methylation of the Sn promoter.
       Accordingly, treatment with 5-azacytidine (AZA), a demethylating agent,
       restored a strong pigmentation pattern that was transmitted to the
       progeny and that was correlated with differential expression of the Sn
       transcript. Genomic sequencing confirmed that methylation of the Sn
       promoter was more apparent in the less pigmented seedlings and was
       greatly reduced in the AZA revertants. In addition, some methylcytosines
       were located in non-symmetrical C sequences. These findings provide an
       insight into Sn and R interaction, a process that we have termed Reduced
       Expression of Endogenous Duplications (REED). We propose that increasing
       the copy number of regulatory genes by endogenous duplication leads to
       such epigenetic mechanisms of silencing. Further understanding of the
       REED process may have broader implications for gene regulation and may
       identify new levels of regulation within eukaryotic genomes.
 DE    Anthocyanins/BIOSYNTHESIS/*GENETICS  Base Sequence
       Corn/*GENETICS/METABOLISM  DNA, Plant/*METABOLISM  Gene Expression
       Regulation, Plant  Gene Products, vpr/*GENETICS/METABOLISM  Genes, Plant
       Methylation  Molecular Sequence Data  Plant
       Proteins/*GENETICS/METABOLISM  Support, Non-U.S. Gov't  Transcription
       Factors/*GENETICS/METABOLISM  JOURNAL ARTICLE

       SOURCE: National Library of Medicine.  NOTICE: This material may be
       protected by Copyright Law (Title 17, U.S.Code).

