Involvement of RelA-associated inhibitor in regulation of trophoblast differentiation via interaction with transcriptional factor specificity protein-1.
Glucose transporter-1 (GLUT1), one of the key functional indicators of placental differentiation, has an important role in placental glucose transport. We previously showed that the protein levels of GLUT1 and nuclear transcription factor specificity protein-1 (Sp1) in rat choriocarcinoma cells (Rcho-1 cells) decreased during the differentiation of these cells to giant cells. We also showed that Sp1 was involved in the regulation of GLUT1 gene expression during this process. RelA-associated inhibitor (RAI) is an inhibitor of nuclear factor-kappaB that was identified by a yeast two-hybrid screen and is preferably expressed in human placenta and heart. RAI was also found to interact with Sp1 and exert an inhibitory effect against the DNA-binding activity of Sp1. We first show here that RAI mRNA expression increased as gestation proceeded and that RAI was localized mainly in the syncytiotrophoblast throughout pregnancy. The chloramphenicol acetyltransferase activity assay in Rcho-1 cells revealed that cotransfection of RAI expression vector resulted in decreased activity of the rat GLUT1 promoter but not in that of a mutated rat GLUT1 promoter lacking the Sp1 binding site. Furthermore, the protein level of RAI increased during differentiation. In addition, transfection of RAI expression vector promoted the morphological differentiation of Rcho-1 cells, and RAI knockdown using RAI-specific small interfering RNA reveals inhibitory effects on the morphological differentiation, as assessed by photomicroscopy. Taken together, these findings suggest that RAI may be involved in the regulation of trophoblast differentiation via interaction with Sp1.
Minekawa
Ryoko
R
Department of Obstetrics and Gynecology, Osaka University Graduate School of Medicine, Osaka, Japan.
Sakata
Masahiro
M
Okamoto
Yoko
Y
Hayashi
Masami
M
Isobe
Aki
A
Takeda
Takashi
T
Yamamoto
Toshiya
T
Koyama
Masayasu
M
Ohmichi
Masahide
M
Tasaka
Keiichi
K
Imai
Kenichi
K
Okamoto
Takashi
T
Murata
Yuji
Y
D000818:Animals; D015153:Blotting, Western; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology*; D045744:Cell Line, Tumor; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental; D051272:Glucose Transporter Type 1 / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D006801:Humans; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D011247:Pregnancy; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D012097:Repressor Proteins; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D014327:Trophoblasts / Q000166:cytology / Q000378:metabolism*
D051272:Glucose Transporter Type 1; D047908:Intracellular Signaling Peptides and Proteins; C119612:PPP1R13L protein, human; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D012097:Repressor Proteins; D016329:Sp1 Transcription Factor; D015500:Chloramphenicol O-Acetyltransferase