A Simple Cipher Governs DNA Recognition by TAL Effectors

Abstract

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.

Plant MicroRNAs Display Differential 3' Truncation and Tailing Modifications That Are ARGONAUTE1 Dependent and Conserved Across Species

“…Two different transcription activator-like effectors, Talc of Xanthomonas oryzae pv oryzicola and Tal9a of X. oryzae pv oryzae, are encoded by two distinct Xanthomonas strains yet share a common target: the promoter of the rice HEN1 gene. These bacterial proteins target different regions of the same promoter, and both effectors dramatically enhance HEN1 expression during infection (Moscou and Bogdanove, 2009). The reason for the induced overexpression of HEN1 is as yet unknown, but perhaps this produces higher levels of HEN1 protein that may alter the relative abundance of miRNAs or other sRNAs significant to host responses.…”

Genome-Edited T Cell Therapies

“…In 2009, two independent research groups detailed the mechanism of TALE DNA recognition [25, 26]. They determined that polymorphisms occurred primarily within hypervariable amino acid residues, located at positions 12 and 13 within each tandem repeat.…”

“…They determined that polymorphisms occurred primarily within hypervariable amino acid residues, located at positions 12 and 13 within each tandem repeat. These residues were termed repeat-variable diresidues (RVDs) and corresponded to a single nucleotide target site [25]. Their codes are well-defined, with NN recognizing G or A, NI for A, HD for C, and NG for T [25, 26].…”

“…These residues were termed repeat-variable diresidues (RVDs) and corresponded to a single nucleotide target site [25]. Their codes are well-defined, with NN recognizing G or A, NI for A, HD for C, and NG for T [25, 26]. More recently, the RVD NH has also been shown to achieve robust guanine-specific recognition [27].…”

L’ingénierie des génomes par les TALEN

“…Les TALE s'associent alors à l'ADN en formant une hélice qui s'enroule autour de l'ADN où chaque répétition reconnaît un nucléotide de la séquence cible ( Figure 1B) [7,8]. Au sein des répétitions, ce sont les acides aminés 12 et 13 qui déterminent la spécificité de liaison aux nucléotides de chacun de ces domaines répétés [9][10][11] (Figure 1C Figure 3B). Ainsi, la technologie d'édition des génomes à l'aide des TALEN, en induisant un grand nombre de modifications génome par réparation de la cassure double-brin [13,18].…”