DNA-binding specificity and molecular functions of NAC transcription factors

TY - JOUR

T1 - DNA-binding specificity and molecular functions of NAC transcription factors

AU - Olsen, Addie Nina

AU - Ernst, Heidi Asschenfeldt

AU - Lo Leggio, Leila

AU - Skriver, Karen

N1 - Keywords: DNA binding; NAC transcription factor; Dimerization; Mutational analysis; Binding site selection

PY - 2005

Y1 - 2005

N2 - The family of NAC (NAM/ATAF1,2/CUC2) transcription factors has been implicated in a wide range of plant processes, but knowledge onthe DNA-binding properties of the family is limited. Using a reiterative selection procedure on random oligonucleotides, we have identifiedconsensus binding sites for two NAC proteins. The consensus sequences are similar, but not identical; both contain the core CGT[GA]. Thestrict consensus sequences, comprising only the most frequent base at each position, are: TTNCGTA and TTGCGTGT. In silico analysis oftarget promoter regions corroborated the selection results. Furthermore, NAC protein binding to the CaMV 35S promoter was shown todepend on sequences similar to the consensus of the selected oligonucleotides. Electrophoretic mobility shift assays demonstrated that NACproteins bind DNA as homo- or heterodimers and that dimerization is necessary for stable DNA binding. The ability of NAC proteins todimerize and to bind DNAwas analysed by structure-based mutagenesis. This identified two salt bridge-forming residues essential for NACprotein dimerization. Alteration of basic residues in a loop region containing several highly conserved residues abolished DNA binding. Thus,the results presented here contribute significantly to our understanding of the specificity and molecular functions of the NAC protein DNAbindingdomain.

AB - The family of NAC (NAM/ATAF1,2/CUC2) transcription factors has been implicated in a wide range of plant processes, but knowledge onthe DNA-binding properties of the family is limited. Using a reiterative selection procedure on random oligonucleotides, we have identifiedconsensus binding sites for two NAC proteins. The consensus sequences are similar, but not identical; both contain the core CGT[GA]. Thestrict consensus sequences, comprising only the most frequent base at each position, are: TTNCGTA and TTGCGTGT. In silico analysis oftarget promoter regions corroborated the selection results. Furthermore, NAC protein binding to the CaMV 35S promoter was shown todepend on sequences similar to the consensus of the selected oligonucleotides. Electrophoretic mobility shift assays demonstrated that NACproteins bind DNA as homo- or heterodimers and that dimerization is necessary for stable DNA binding. The ability of NAC proteins todimerize and to bind DNAwas analysed by structure-based mutagenesis. This identified two salt bridge-forming residues essential for NACprotein dimerization. Alteration of basic residues in a loop region containing several highly conserved residues abolished DNA binding. Thus,the results presented here contribute significantly to our understanding of the specificity and molecular functions of the NAC protein DNAbindingdomain.

U2 - 10.1016/j.plantsci.2005.05.035

DO - 10.1016/j.plantsci.2005.05.035

M3 - Journal article

SN - 0168-9452

VL - 169

SP - 785

EP - 797

JO - Plant Science

JF - Plant Science

IS - 4

ER -