Transcription activator-like （TAL） effectors specifically bind to double stranded （ds） DNA through a central domain of tandem repeats. Each TAL effector （TALE） repeat comprises 33-35 amino acids and recognizes o...Transcription activator-like （TAL） effectors specifically bind to double stranded （ds） DNA through a central domain of tandem repeats. Each TAL effector （TALE） repeat comprises 33-35 amino acids and recognizes one specific DNA base through a highly variable residue at a fixed position in the repeat. Structural studies have revealed the molecular basis of DNA recognition by TALE repeats. Examination of the overall structure reveals that the basic building block of TALE protein, namely a helical hairpin, is one-helix shifted from the previously defined TALE motif. Here we wish to suggest a structure-based re-demarcation of the TALE repeat which starts with the residues that bind to the DNA backbone phosphate and concludes with the base-rec- ognition hyper-variable residue. This new numbering system is consistent with the （=-solenoid superfamily to which TALE belongs, and reflects the structural integrity of TAL effectors. In addition, it confers integral number of TALE repeats that matches the number of bound DNA bases. We then present fifteen crystal structures of engineered dHax3 variants in complex with target DNA molecules, which elucidate the structural basis for the recognition of bases adenine （A） and guanine （G） by reported or uncharacterized TALE codes. Finally, we analyzed the sequence-structure correlation of the amino acid residues within a TALE repeat. The structural analyses reported here may advance the mechanistic understanding of TALE proteins and facilitate the design of TALEN with improved affinity and specificity.展开更多
Manipulation of gene expression through targeting specific DNA or RNA sequences is a significant challenge, tn the past decade, transcription activator-like （TAL） effectors and zinc fingers （ZFs） have been success...Manipulation of gene expression through targeting specific DNA or RNA sequences is a significant challenge, tn the past decade, transcription activator-like （TAL） effectors and zinc fingers （ZFs） have been successfully developed into useful tools for DNA recognition （Bogdanove and Voytas, 2011; Deng et al., 2012a, 2012b）. However, little progress has been made in the realm of RNA targeting due to the lack of understanding about the modular RNA recognition mechanism.展开更多
基金ACKNOWLEDGEMENTS We apologize to colleagues whose work could not be cited due to the scope of this review. We would like to thank members in Yan laboratory for discussions. We thank Brendan Lehnert, Xinlei Sheng, Quanxiu Li, Dan Ma and Xinhui Zhou for critical reading. This work was supported by funds from the National Basic Research Program （973 Program） （No. 2011CB910501）, the National Natural Science Foundation of China （Grant Nos. 31321062-20131319400, 31125009, and 91017011 ）, and funds from Tsinghua-Peking Center for Life Sciences. The research of N.Y. was supported in part by an International Early Career Scientist grant from the Howard Hughes Medical Institute.
文摘Transcription activator-like （TAL） effectors specifically bind to double stranded （ds） DNA through a central domain of tandem repeats. Each TAL effector （TALE） repeat comprises 33-35 amino acids and recognizes one specific DNA base through a highly variable residue at a fixed position in the repeat. Structural studies have revealed the molecular basis of DNA recognition by TALE repeats. Examination of the overall structure reveals that the basic building block of TALE protein, namely a helical hairpin, is one-helix shifted from the previously defined TALE motif. Here we wish to suggest a structure-based re-demarcation of the TALE repeat which starts with the residues that bind to the DNA backbone phosphate and concludes with the base-rec- ognition hyper-variable residue. This new numbering system is consistent with the （=-solenoid superfamily to which TALE belongs, and reflects the structural integrity of TAL effectors. In addition, it confers integral number of TALE repeats that matches the number of bound DNA bases. We then present fifteen crystal structures of engineered dHax3 variants in complex with target DNA molecules, which elucidate the structural basis for the recognition of bases adenine （A） and guanine （G） by reported or uncharacterized TALE codes. Finally, we analyzed the sequence-structure correlation of the amino acid residues within a TALE repeat. The structural analyses reported here may advance the mechanistic understanding of TALE proteins and facilitate the design of TALEN with improved affinity and specificity.
基金This work was funded by the National Natural Science Foundation of China （Program No. 31200567）, the Fundamental Research Funds for the Central Universities （Program No. 2014JQ001）, and the Huazhong Agricultural University Scientific ＆ Technological Self-innovation Foundation （Program No. 2013RC013）.ACKNOWLEDGMENTS No conflict of interest declared.
文摘Manipulation of gene expression through targeting specific DNA or RNA sequences is a significant challenge, tn the past decade, transcription activator-like （TAL） effectors and zinc fingers （ZFs） have been successfully developed into useful tools for DNA recognition （Bogdanove and Voytas, 2011; Deng et al., 2012a, 2012b）. However, little progress has been made in the realm of RNA targeting due to the lack of understanding about the modular RNA recognition mechanism.
