This Article Full Text Full Text (PDF) Data Supplement All Versions of this Article: 102/6/661    most recent CIRCRESAHA.107.165134v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Tang, Y. Articles by Liaw, L. Search for Related Content PubMed PubMed Citation Articles by Tang, Y. Articles by Liaw, L. Related Collections Cell biology/structural biology Cell signalling/signal transduction Gene expression Smooth muscle proliferation and differentiation

(Circulation Research. 2008;102:661.)
© 2008 American Heart Association, Inc.

Molecular Medicine

Hairy-Related Transcription Factors Inhibit Notch-Induced Smooth Muscle -Actin Expression by Interfering With Notch Intracellular Domain/CBF-1 Complex Interaction With the CBF-1–Binding Site

Yuefeng Tang, Sumithra Urs, Lucy Liaw

From the Center for Molecular Medicine, Maine Medical Center Research Institute, Scarborough.

Correspondence to Lucy Liaw, PhD, Center for Molecular Medicine, Maine Medical Center Research Institute, 81 Research Dr, Scarborough, ME 04074. E-mail liawl{at}mmc.org

Notch signaling regulates smooth muscle cell phenotype and is critical for vascular development. One Notch target is smooth muscle -actin (SMA), a differentiated smooth muscle cell marker. The Notch intracellular domain (NotchICD) forms a complex with CBF-1 (C-promoter–binding factor-1) and directly induces SMA expression. Using primary human smooth muscle cells, we show that expression of the constitutive active ICD of human Notch1, Notch2, or Notch4 receptors increase SMA levels. NotchICD also induce expression of the transcriptional repressors HRT1 (Hairy-related transcription factor 1) and HRT2, in a CBF-1–dependent manner. However, unlike the activating effects of NotchICD, HRT1 or HRT2 represses basal SMA expression, and both are strong antagonists of NotchICD-induced SMA upregulation. This antagonism does not depend on histone deacetylase activity and occurs at the transcriptional level. Competitive coimmunoprecipitation experiments demonstrate that HRT does not disrupt the association of NotchICD and CBF-1, which form a complex in the presence or absence of HRTs. However, HRT suppresses NotchICD/CBF-1 binding to the SMA promoter, as measured by chromatin immunoprecipitation, and transactivation of an SMA promoter reporter spanning sequences –124/+32. SMA expression was regulated similarly following endogenous Notch activation in smooth muscle cells by coculture with endothelial cells, and this effect was also sensitive to HRT inhibition. Temporally defined HRT activity may constitute a negative feedback mechanism of Notch signaling. Our study presents a novel mechanism by which a balance between Notch signaling and HRT activity determines the expression of smooth muscle differentiation markers including SMA.

Key Words: vascular smooth muscle cells • smooth muscle -actin • signaling pathways • endothelial cells

This article has been cited by other articles:

				T. Liu, B. Hu, Y. Y. Choi, M. Chung, M. Ullenbruch, H. Yu, J. B. Lowe, and S. H. Phan Notch1 Signaling in FIZZ1 Induction of Myofibroblast Differentiation Am. J. Pathol., May 1, 2009; 174(5): 1745 - 1755. [Abstract] [Full Text] [PDF]

				J. N. Regan and M. W. Majesky Building a Vessel Wall With Notch Signaling Circ. Res., February 27, 2009; 104(4): 419 - 421. [Full Text] [PDF]

				H. Liu, S. Kennard, and B. Lilly NOTCH3 Expression Is Induced in Mural Cells Through an Autoregulatory Loop That Requires Endothelial-Expressed JAGGED1 Circ. Res., February 27, 2009; 104(4): 466 - 475. [Abstract] [Full Text] [PDF]

				M. Shin, H. Nagai, and G. Sheng Notch mediates Wnt and BMP signals in the early separation of smooth muscle progenitors and blood/endothelial common progenitors Development, February 15, 2009; 136(4): 595 - 603. [Abstract] [Full Text] [PDF]

				D. Morrow, S. Guha, C. Sweeney, Y. Birney, T. Walshe, C. O'Brien, D. Walls, E. M. Redmond, and P. A. Cahill Notch and Vascular Smooth Muscle Cell Phenotype Circ. Res., December 5, 2008; 103(12): 1370 - 1382. [Abstract] [Full Text] [PDF]

				D. A. Venkatesh, K.-S. Park, A. Harrington, L. Miceli-Libby, J. K. Yoon, and L. Liaw Cardiovascular and Hematopoietic Defects Associated With Notch1 Activation in Embryonic Tie2-Expressing Populations Circ. Res., August 15, 2008; 103(4): 423 - 431. [Abstract] [Full Text] [PDF]