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Present address: Sainsbury Laboratory, John Innes Centre, Norwich, Norfolk NR4 7UH, UK.

Present address: Icon Genetics GmbH, Biozentrum, Weinbergweg 22, D-06120 Halle (Saale), Germany.

^* To whom correspondence should be addressed. E-mail: jens.boch@genetik.uni-halle.de

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Originally published in Science Express on 29 October 2009

Science 11 December 2009:

Vol. 326. no. 5959, p. 1501

DOI: 10.1126/science.1178817

BREVIA

A Simple Cipher Governs DNA Recognition by TAL Effectors

Matthew J. Moscou and Adam J. Bogdanove^*

TAL effectors of plant pathogenic bacteria in the genus Xanthomonas bind host DNA and activate genes that contribute to disease or turn on defense. Target specificity depends on an effector-variable number of typically 34 amino acid repeats, but the mechanism of recognition is not understood. We show that a repeat-variable pair of residues specifies the nucleotides in the target site, one pair to one nucleotide, with no apparent context dependence. Our finding represents a previously unknown mechanism for protein-DNA recognition that explains TAL effector specificity, enables target site prediction, and opens prospects for use of TAL effectors in research and biotechnology.

Department of Plant Pathology and Bioinformatics and Computational Biology Program, Iowa State University, Ames, IA 50011, USA.

^* To whom correspondence should be addressed. E-mail: ajbog@iastate.edu

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Science 11 December 2009:

Vol. 326. no. 5959, pp. 1491 - 1492

DOI: 10.1126/science.1183604

PERSPECTIVES

PLANT SCIENCE:

DNA Binding Made Easy

Daniel F. Voytas¹ and J. Keith Joung^2,3,4

All cells encode specific DNA binding proteins that ensure that genetic material is appropriately expressed, replicated, and transmitted from one generation to the next. Mother Nature solved the DNA recognition problem by inventing a handful of protein motifs, including the zinc finger, the helix-turn-helix, and the leucine zipper. As is the case with all good solutions to a problem, these motifs are used over and over again in biological systems; for example, DNA binding proteins containing the helix-turn-helix motif are found in both prokaryotes and eukaryotes, and zinc finger—containing proteins are the most abundant protein class encoded by the human genome. It is surprising, therefore, to learn from studies by Boch et al. (1) on page 1509 and Moscou and Bogdanove (2) on page 1501 of this issue, about a new DNA binding motif that has heretofore escaped description.

¹ Department of Genetics, Cell Biology and Development and Center for Genome Engineering, University of Minnesota, Minneapolis, MN 55455, USA.

² Molecular Pathology Unit and Center for Cancer Research, Massachusetts General Hospital, Charlestown, MA 02129, USA.

³ Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, MA 02114, USA.

⁴ Department of Pathology, Harvard Medical School, Boston, MA 02115, USA.

E-mail: voytas@umn.edu

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