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Open Access Research article

Mapping and functional characterization of the murine Smoothelin-like 1 promoter

Annegret Ulke-Lemée, Sara R Turner, Saad H Mughal, Meredith A Borman, Robert J Winkfein and Justin A MacDonald*

Author Affiliations

Smooth Muscle Research Group and Department of Biochemistry & Molecular Biology, University of Calgary, 3280 Hospital Drive NW, Calgary, Alberta, T2N 4Z6, Canada

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BMC Molecular Biology 2011, 12:10  doi:10.1186/1471-2199-12-10

Published: 27 February 2011

Abstract

Background

Smoothelin-like 1 (SMTNL1, also known as CHASM) plays a role in promoting relaxation as well as adaptive responses to exercise, pregnancy and sexual development in smooth and skeletal muscle. Investigations of Smtnl1 transcriptional regulation are still lacking. Thus, in this study, we identify and characterize key regulatory elements of the mouse Smtnl1 gene.

Results

We mapped the key regulatory elements of the Smtnl1 promoter region: the transcriptional start site (TSS) lays -44 bp from the translational start codon and a TATA-box motif at -75 bp was conserved amongst all mammalian Smtnl1 promoters investigated. The Smtnl1 proximal promoter enhances expression up to 8-fold in smooth muscle cells and a second activating region lays 500 bp further upstream. Two repressing motifs were present (-118 to -218 bp and -1637 to -1869 bp). The proximal promoter is highly conserved in mammals and contains a mirror repeat sequence. In silico analysis suggests many transcription factors (notably MyoD) could potentially bind within the Smtnl1 proximal promoter sequence.

Conclusion

Smtnl1 transcript was identified in all smooth muscle tissues examined to date, albeit at much lower levels than found in skeletal muscle. It is unlikely that multiple SMTNL1 isoforms exist since a single Smtnl1 transcription start site was identified in both skeletal and intestinal smooth muscle. Promoter studies suggest restrictive control of Smtnl1 expression in non-muscle cells.