TIP27: a novel repressor of the nuclear orphan receptor TAK1/TR4.
The nuclear orphan receptor TAK1/TR4 functions as a positive as well as a negative regulator of transcription; however, little is known about the factors regulating or mediating its activity. Yeast two-hybrid analysis using the ligand-binding domain (LBD) of TAK1 as bait identified a novel TAK1-interacting protein, referred to as TIP27, which functions as a repressor of TAK1-mediated transactivation. TIP27 is a 27 kDa protein containing two zinc finger motifs. Mammalian two-hybrid analysis showed that TIP27 interacts specifically with TAK1 and not with several other nuclear receptors tested. The region between Asp39 and Lys79 of TIP27, referred to as TAK1-interaction domain (TID), is critical for its interaction with TAK1 while the TAK1-LBD from helix 3 until the C-terminus is required for the optimal interaction with TIP27. Pull-down assays demonstrated that the TIP27 physically interacts with TAK1 and supported the critical importance of the TID. Confocal microscopy showed that in the nucleus, TIP27 and TAK1 co-localize. TIP27 acts as a strong repressor of DR1-dependent transcriptional activation by TAK1. This repression does not involve the inhibition of TAK1 homodimerization or DR1 binding but may be due to an effect on co-activator recruitment by TAK1. Our results indicate that TIP27 functions as a TAK1-selective repressor.
Nakajima
Takeshi
T
Cell Biology Section, Division of Intramural Research, National Institute of Environmental Health Sciences, National Institutes of Health, 111 T.W. Alexander Drive, Research Triangle Park, NC 27709, USA.
Fujino
Sanae
S
Nakanishi
Gen
G
Kim
Yong-Sik
YS
Jetten
Anton M
AM
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000737:chemistry; D056970:Co-Repressor Proteins; D004268:DNA-Binding Proteins; D005786:Gene Expression Regulation; D006801:Humans; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000032:analysis / Q000737:chemistry / Q000502:physiology*; D017434:Protein Structure, Tertiary; D011987:Receptors, Steroid / Q000032:analysis / Q000378:metabolism*; D011988:Receptors, Thyroid Hormone / Q000032:analysis / Q000378:metabolism*; D012097:Repressor Proteins / Q000032:analysis / Q000737:chemistry / Q000502:physiology*; D014018:Tissue Distribution; D020798:Two-Hybrid System Techniques
D056970:Co-Repressor Proteins; D004268:DNA-Binding Proteins; C430460:JAZF1 protein, human; C490515:NR2C2 protein, human; D009363:Neoplasm Proteins; D011987:Receptors, Steroid; D011988:Receptors, Thyroid Hormone; D012097:Repressor Proteins