Smooth Muscle Cell Phenotype-dependent Transcriptional Regulation of the α1 Integrin Gene*
- Hideto Obata,
- Ken’ichiro Hayashi,
- Wataru Nishida,
- Takuya Momiyama,
- Atsumasa Uchida‡,
- Takahiro Ochi§ and
- Kenji Sobue¶
- From the Department of Neurochemistry and Neuropharmacology, Biomedical Research Center, and the §Department of Orthopaedic Surgery, Osaka University Medical School, 2-2 Yamadaoka, Suita, Osaka 565, and the ‡Department of Orthopaedic Surgery, Mie University Medical School, 2-174 Edobashi, Tsu, Mie 514, Japan
Abstract
The expressional regulation of chicken α1 integrin in smooth muscle cells was studied. The α1 integrin mRNA was expressed developmentally and was distributed dominantly in vascular and visceral smooth muscles in chick embryos. In a primary culture of smooth muscle cells, α1 integrin expression was dramatically down-regulated during serum-induced dedifferentiation. Promoter analyses revealed that the 5′-upstream region (−516 to +281) was sufficient for transcriptional activation in differentiated smooth muscle cells but not in dedifferentiated smooth muscle cells or chick embryo fibroblasts. Like other α integrin promoters, the promoter region of the α1 integrin gene lacks TATA and CCAAT boxes and contains binding sites for AP1 and AP2. The essential difference from other α integrin promoters is the presence of a CArG box-like motif. Deletion and site-directed mutation analyses revealed that the CArG box-like motif was an essential cis-element for transcriptional activation in differentiated smooth muscle cells, whereas the binding sites for AP1 and AP2 were not. Using specific antibodies, a nuclear protein factor specifically bound to the CArG box-like motif was identified as serum response factor. These results indicate that α1 integrin expression in smooth muscle cells is regulated transcriptionally in a phenotype-dependent manner and that serum response factor binding plays a crucial role in this regulation.
Footnotes
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↵* This work was supported by grants-in-aid for COE research from the Ministry of Education, Science, Sports, and Culture of Japan (to K. S.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) AB000470 and AB000471.
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↵¶ To whom correspondence should be addressed. Tel.: 81-6-879-3680; Fax: 81-6-879-3689; E-mail:sobue{at}nbiochem.med.osaka-u.ac.jp.
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↵1 The abbreviations used are: SMC(s), smooth muscle cell(s); CaD, caldesmon; RACE, rapid amplification of cDNA end; PCR, polymerase chain reaction; kbp, kilobase pair(s); CEFs, chick embryo fibroblasts; SRF, serum response factor; bp, base pair(s); PIPES, piperazine-N,N′-bis(2-ethanesulfonic acid); CAT, chloramphenicol acetyltransferase; SRE, serum response element.
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- Received January 27, 1997.
- Revision received June 19, 1997.
