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Nuclear import and DNA binding of the ZHD5 transcription factor is modulated by a competitive peptide inhibitor in Arabidopsis.

Hong SY, Kim OK, Kim SG, Yang MS, Park CM - J. Biol. Chem. (2010)

Bottom Line: Accordingly, the transcriptional activation activity of ZHD5 was significantly suppressed by MIF1 coexpressed transiently in Arabidopsis protoplasts.Transgenic plants overexpressing the ZHD5 gene (35S:ZHD5) exhibited accelerated growth with larger leaves.These observations indicate that MIF1 regulates the ZHD5 activities in a dual step manner: nuclear import and DNA binding.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Seoul National University, Seoul 151-742, Korea.

ABSTRACT
Competitive inhibition of transcription factors by small proteins is an intriguing component of gene regulatory networks in both animals and plants. The small interfering proteins possess limited sequence homologies to specific transcription factors but lack one or more protein motifs required for transcription factor activities. They interfere with the activities of transcription factors, such as DNA binding and transcriptional activation, by forming nonfunctional heterodimers. A potential example is the Arabidopsis MIF1 (mini zinc finger 1) protein consisting of 101 residues. It has a zinc finger domain but lacks other protein motifs normally present in transcription factors. In this work, we show that MIF1 and its functional homologues physically interact with a group of zinc finger homeodomain (ZHD) transcription factors, such as ZHD5, that regulate floral architecture and leaf development. Gel mobility shift assays revealed that MIF1 blocks the DNA binding activity of ZHD5 homodimers by competitively forming MIF1-ZHD5 heterodimers. Accordingly, the transcriptional activation activity of ZHD5 was significantly suppressed by MIF1 coexpressed transiently in Arabidopsis protoplasts. Notably, MIF1 also prevents ZHD5 from nuclear localization. Although ZHD5 was localized exclusively in the nucleus, it was scattered throughout the cytoplasm when MIF1 was coexpressed. Transgenic plants overexpressing the ZHD5 gene (35S:ZHD5) exhibited accelerated growth with larger leaves. Consistent with the negative regulation of ZHD5 by MIF1, the 35S:ZHD5 phenotypes were diminished by MIF1 coexpression. These observations indicate that MIF1 regulates the ZHD5 activities in a dual step manner: nuclear import and DNA binding.

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Yeast two-hybrid assays on the MIF-ZHD interactions. The MIF-ZHD interactions were examined by yeast two-hybrid assays. Relative strengths of the interactions are indicated. +++, very strong; ++, moderate; +, weak; −, no interaction.
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Figure 1: Yeast two-hybrid assays on the MIF-ZHD interactions. The MIF-ZHD interactions were examined by yeast two-hybrid assays. Relative strengths of the interactions are indicated. +++, very strong; ++, moderate; +, weak; −, no interaction.

Mentions: We first examined whether the MIF proteins interact with the ZHD proteins by yeast two-hybrid assays using the MIF proteins as baits and the ZHD proteins as preys. We determined the relative strengths of the interactions by measuring cell densities. As inferred from the protein structural analysis, the MIF proteins interacted with a subset of the ZHD proteins. Notably, the interaction patterns were quite diverse. The MIF proteins interacted strongly with ZHD5, ZHD8, ZHD10, and ZHD13 (Fig. 1). In contrast, they did not exhibit any discernible interactions with ZHD4, ZHD11, ZHD12, and ZHD14. Although MIF2 and MIF3 interacted with ZHD3, MIF1 did not. In addition, only MIF3 showed measurable interaction with ZHD9.


Nuclear import and DNA binding of the ZHD5 transcription factor is modulated by a competitive peptide inhibitor in Arabidopsis.

Hong SY, Kim OK, Kim SG, Yang MS, Park CM - J. Biol. Chem. (2010)

Yeast two-hybrid assays on the MIF-ZHD interactions. The MIF-ZHD interactions were examined by yeast two-hybrid assays. Relative strengths of the interactions are indicated. +++, very strong; ++, moderate; +, weak; −, no interaction.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3020774&req=5

Figure 1: Yeast two-hybrid assays on the MIF-ZHD interactions. The MIF-ZHD interactions were examined by yeast two-hybrid assays. Relative strengths of the interactions are indicated. +++, very strong; ++, moderate; +, weak; −, no interaction.
Mentions: We first examined whether the MIF proteins interact with the ZHD proteins by yeast two-hybrid assays using the MIF proteins as baits and the ZHD proteins as preys. We determined the relative strengths of the interactions by measuring cell densities. As inferred from the protein structural analysis, the MIF proteins interacted with a subset of the ZHD proteins. Notably, the interaction patterns were quite diverse. The MIF proteins interacted strongly with ZHD5, ZHD8, ZHD10, and ZHD13 (Fig. 1). In contrast, they did not exhibit any discernible interactions with ZHD4, ZHD11, ZHD12, and ZHD14. Although MIF2 and MIF3 interacted with ZHD3, MIF1 did not. In addition, only MIF3 showed measurable interaction with ZHD9.

Bottom Line: Accordingly, the transcriptional activation activity of ZHD5 was significantly suppressed by MIF1 coexpressed transiently in Arabidopsis protoplasts.Transgenic plants overexpressing the ZHD5 gene (35S:ZHD5) exhibited accelerated growth with larger leaves.These observations indicate that MIF1 regulates the ZHD5 activities in a dual step manner: nuclear import and DNA binding.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Seoul National University, Seoul 151-742, Korea.

ABSTRACT
Competitive inhibition of transcription factors by small proteins is an intriguing component of gene regulatory networks in both animals and plants. The small interfering proteins possess limited sequence homologies to specific transcription factors but lack one or more protein motifs required for transcription factor activities. They interfere with the activities of transcription factors, such as DNA binding and transcriptional activation, by forming nonfunctional heterodimers. A potential example is the Arabidopsis MIF1 (mini zinc finger 1) protein consisting of 101 residues. It has a zinc finger domain but lacks other protein motifs normally present in transcription factors. In this work, we show that MIF1 and its functional homologues physically interact with a group of zinc finger homeodomain (ZHD) transcription factors, such as ZHD5, that regulate floral architecture and leaf development. Gel mobility shift assays revealed that MIF1 blocks the DNA binding activity of ZHD5 homodimers by competitively forming MIF1-ZHD5 heterodimers. Accordingly, the transcriptional activation activity of ZHD5 was significantly suppressed by MIF1 coexpressed transiently in Arabidopsis protoplasts. Notably, MIF1 also prevents ZHD5 from nuclear localization. Although ZHD5 was localized exclusively in the nucleus, it was scattered throughout the cytoplasm when MIF1 was coexpressed. Transgenic plants overexpressing the ZHD5 gene (35S:ZHD5) exhibited accelerated growth with larger leaves. Consistent with the negative regulation of ZHD5 by MIF1, the 35S:ZHD5 phenotypes were diminished by MIF1 coexpression. These observations indicate that MIF1 regulates the ZHD5 activities in a dual step manner: nuclear import and DNA binding.

Show MeSH