Open AccessTransgenic expression of CBBP, a CXC domain protein, establishes paramutation in maize
Author(s) -
Katarzyna Brzeska,
Jan Brzeski,
Jacquelyn Smith,
Vicki L. Chandler
Publication year - 2010
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.1001576107
Subject(s) - biology , genetics , gene silencing , chromatin , heterochromatin , locus (genetics) , transgene , gene , tandem repeat , genome
Paramutation is the ability of specific DNA sequences to communicate in trans to establish meiotically heritable expression states. Paramutation at the maizeb1 locus is mediated by seven unique noncoding transcribed tandem repeats of 853 bp that are required to establish and maintain the meiotically heritable expression and distinct chromatin states associated withb1 paramutation. In this study, we report the identification of a CXC-domain protein CBBP (CXC domainb1 -repeat binding protein) that binds to a defined region within theb1 tandem repeat sequence in vivo and in vitro. When CBBP is expressed from a transgene in maize, it can induce a silent state at theb1 locus that is heritable in progeny no longer containing the transgene, and the silent epiallele is capable of silencing an active epiallele, characteristic of paramutation. Accumulation of the CBBP protein correlates withb1 silencing in transgenic and nontransgenic plants. The ability of CBBP to form multimers and to bind to theb1 tandem repeats suggests a model for counting the number ofb1 repeats. In contrast to previously identified proteins involved in paramutation, CBBP does not share similarity to the known components of theArabidopsis RNAi heterochromatin silencing pathway. Thus, this study defines another class of protein that is involved in heritable gene silencing.