TY - JOUR

T1 - Senescence-associated barley NAC (NAM, ATAF1,2, CUC) transcription factor interacts with radical-induced cell death 1 through a disordered regulatory domain

AU - Kjaersgaard, Trine

AU - Jensen, Michael K

AU - Christiansen, Michael W

AU - Gregersen, Per L.

AU - Kragelund, Birthe B

AU - Skriver, Karen

PY - 2011

Y1 - 2011

N2 - Senescence in plants involves massive nutrient relocation and age-related cell death. Characterization of the molecular components, such as transcription factors (TFs), involved in these processes is required to understand senescence. We found that HvNAC005 and HvNAC013 of the plant-specific NAC (NAM, ATAF1,2, CUC) TF family are up-regulated during senescence in barley (Hordeum vulgare). Both HvNAC005 and HvNAC013 bound the conserved NAC DNA target sequence. Computational and biophysical analyses showed that both proteins are intrinsically disordered in their large C-terminal domains, which are transcription regulatory domains (TRDs) in many NAC TFs. Using motif searches and interaction studies in yeast we identified an evolutionarily conserved sequence, the LP motif, in the TRD of HvNAC013. This motif was sufficient for transcriptional activity. In contrast, HvNAC005 did not function as a transcriptional activator suggesting that an involvement of HvNAC013 and HvNAC005 in senescence will be different. HvNAC013 interacted with barley radical-induced cell death 1 (RCD1) via the very C-terminal part of its TRD, outside of the region containing the LP motif. No significant secondary structure was induced in the HvNAC013 TRD upon interaction with RCD1. RCD1 also interacted with regions dominated by intrinsic disorder in TFs of the MYB and basic helix-loop-helix families. We propose that RCD1 is a regulatory protein capable of interacting with many different TFs by exploiting their intrinsic disorder. In addition, we present the first structural characterization of NAC C-terminal domains and relate intrinsic disorder and sequence motifs to activity and protein-protein interactions.

AB - Senescence in plants involves massive nutrient relocation and age-related cell death. Characterization of the molecular components, such as transcription factors (TFs), involved in these processes is required to understand senescence. We found that HvNAC005 and HvNAC013 of the plant-specific NAC (NAM, ATAF1,2, CUC) TF family are up-regulated during senescence in barley (Hordeum vulgare). Both HvNAC005 and HvNAC013 bound the conserved NAC DNA target sequence. Computational and biophysical analyses showed that both proteins are intrinsically disordered in their large C-terminal domains, which are transcription regulatory domains (TRDs) in many NAC TFs. Using motif searches and interaction studies in yeast we identified an evolutionarily conserved sequence, the LP motif, in the TRD of HvNAC013. This motif was sufficient for transcriptional activity. In contrast, HvNAC005 did not function as a transcriptional activator suggesting that an involvement of HvNAC013 and HvNAC005 in senescence will be different. HvNAC013 interacted with barley radical-induced cell death 1 (RCD1) via the very C-terminal part of its TRD, outside of the region containing the LP motif. No significant secondary structure was induced in the HvNAC013 TRD upon interaction with RCD1. RCD1 also interacted with regions dominated by intrinsic disorder in TFs of the MYB and basic helix-loop-helix families. We propose that RCD1 is a regulatory protein capable of interacting with many different TFs by exploiting their intrinsic disorder. In addition, we present the first structural characterization of NAC C-terminal domains and relate intrinsic disorder and sequence motifs to activity and protein-protein interactions.

KW - Cell Aging

KW - Evolution, Molecular

KW - Helix-Loop-Helix Motifs

KW - Hordeum

KW - Nuclear Proteins

KW - Plant Proteins

KW - Protein Structure, Tertiary

KW - Transcription Factors

U2 - 10.1074/jbc.M111.247221

DO - 10.1074/jbc.M111.247221

M3 - Journal article

C2 - 21856750

VL - 286

SP - 35418

EP - 35429

JO - Journal of Biological Chemistry

JF - Journal of Biological Chemistry

SN - 0021-9258

IS - 41

ER -