Ternary complex formation between MADS-box transcription factors and the histone fold protein NF-YB.
MADS-box proteins are transcription factors present in different eukaryotic kingdoms. In contrast to plants, for mammalian and yeast MADS-box proteins ternary complex formation with unrelated transcription factors was reported. We show here the first identification of such ternary interaction in plants. A rice seed-specific NF-YB was identified as partner of OsMADS18 by two-hybrid screening. NF-YB contains a histone fold motif, HFM,(1) and is part of the trimeric CCAAT-binding NF-Y complex. OsMADS18, alone or in combination with a natural partner, interacts with OsNF-YB1 through the MADS and I regions. The mouse NF-YB also associates with OsMADS18 in vivo and in vitro as a NF-YB-NF-YC dimer. Other rice MADS-box proteins do not interact in these assays, indicating specificity for the interaction. OsNF-YB1 is capable of heterodimerizing with NF-YC, but not trimerizing with NF-YA, thus precluding CCAAT binding. Mutation of the variant Asp at position 99 of the HFM alpha2-helix into a conserved serine recovers the capacity to interact with NF-YA, but not with DNA. This is the first indication that members of the NF-YB family work through mechanisms independent of the CCAAT box.
Masiero
Simona
S
Dipartimento di Genetica e Biologia dei Microrganismi, Universitá di Milano, Via Celoria 26, 20133 Milano, Italy.
Imbriano
Carol
C
Ravasio
Federica
F
Favaro
Rebecca
R
Pelucchi
Nilla
N
Gorla
Mirella Sari
MS
Mantovani
Roberto
R
Colombo
Lucia
L
Kater
Martin M
MM
D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis; D023081:CCAAT-Binding Factor / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D026161:MADS Domain Proteins / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011817:Rabbits; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D014157:Transcription Factors; D020798:Two-Hybrid System Techniques
D023081:CCAAT-Binding Factor; D004268:DNA-Binding Proteins; D026161:MADS Domain Proteins; C492060:Nfya protein, mouse; C492062:Nfyb protein, mouse; D010940:Plant Proteins; D014157:Transcription Factors