Identification and functional analysis of Zranb2 as a novel Smad-binding protein that suppresses BMP signaling.
Smads 1/5/8 transduce the major intracellular signaling of bone morphogenetic proteins (BMPs). In the present study, we analyzed Smad1-binding proteins in HEK293T cells using a proteomic technique and identified the protein, zinc-finger, RAN-binding domain-containing protein 2 (ZRANB2). Zranb2 interacted strongly with Smad1, Smad5, and Smad8 and weakly with Smad4. The overexpression of Zranb2 inhibited BMP activities in C2C12 myoblasts in vitro, and the injection of Zranb2 mRNA into zebrafish embryos induced weak dorsalization. Deletion analyses of Zranb2 indicated that the serine/arginine-rich (SR) domain and the glutamine-rich domain were required for the inhibition of BMP activity and the interaction with Smad1, respectively. Zranb2 was found to be localized in the nucleus; however, the SR domain-deleted mutant localized to the cytoplasm. The knockdown of endogenous Zranb2 in C2C12 cells enhanced BMP activity. Zranb2 suppressed Smad transcriptional activity without affecting Smad phosphorylation, nuclear localization, or DNA binding. Taken together, these findings suggested that Zranb2 is a novel BMP suppressor that forms a complex with Smads in the nucleus.
Division of Pathophysiology, Research Center for Genomic Medicine, Saitama Medical University, 1397-1 Yamane, Hidaka-shi, Saitama, 350-1241, Japan.
Satoshi
S
Ohte
Shoichiro
S
Kokabu
Shun-ichiro
S
Iemura
Hiroki
H
Sasanuma
Katsumi
K
Yoneyama
Masashi
M
Shin
Seiya
S
Suzuki
Toru
T
Fukuda
Yukio
Y
Nakamura
Eijiro
E
Jimi
Toru
T
Natsume
Takenobu
T
Katagiri
D000595:Amino Acid Sequence; D000818:Animals; D055415:Bone Morphogenetic Protein 4 / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D015398:Signal Transduction; D051785:Smad Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014158:Transcription, Genetic
D055415:Bone Morphogenetic Protein 4; D016601:RNA-Binding Proteins; D051785:Smad Proteins; C486374:Zranb2 protein, mouse; D004247:DNA