Publications (3)4.57 Total impact
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ABSTRACT: Activation of transforming growth factor β receptors causes the phosphorylation and nuclear translocation of Smad proteins, which then participate in the regulation of expression of target genes. We describe a novel Smad-interacting protein, SIP1, which was identified using the yeast two-hybrid system. Although SIP1 interacts with the MH2 domain of receptor-regulated Smads in yeast andin vitro, its interaction with full-length Smads in mammalian cells requires receptor-mediated Smad activation. SIP1 is a new member of the δEF1/Zfh-1 family of two-handed zinc finger/homeodomain proteins. Like δEF1, SIP1 binds to 5′-CACCT sequences in different promoters, including the Xenopus brachyury promoter. Overexpression of either full-length SIP1 or its C-terminal zinc finger cluster, which bind to the Xbra2promoter in vitro, prevented expression of the endogenousXbra gene in early Xenopus embryos. Therefore, SIP1, like δEF1, is likely to be a transcriptional repressor, which may be involved in the regulation of at least one immediate response gene for activin-dependent signal transduction pathways. The identification of this Smad-interacting protein opens new routes to investigate the mechanisms by which transforming growth factor β members exert their effects on expression of target genes in responsive cells and in the vertebrate embryo.
Chapter: Heart Development in Drosophila[Show abstract] [Hide abstract]
ABSTRACT: This chapter describes the development of heart in Drosophila. The Drosophila heart or dorsal vessel is a simple tubular structure that forms at the dorsal midline of the embryo and pumps the hemolymph (including the blood cells) through the body cavity in an open circulatory system. The heart consists of two major cell types: the inner, contractile muscle cells (the “cardial” or “myocardial” cells) are aligned in two rows flanked on each side by an outer row of pericardial cells. The two rows of cardial cells form a central cavity, generating the lumen of the heart. Anterior pericardial cells form the blood-forming organs during larval stages. An emerging genetic cascade of mesoderm intrinsic factors (from twist to tinrnan to zfh-1 and finally to eve) and extrinsic signals (gene decapentaplegic, dpp and gene wingless, wg) specifies the sequential subdivisions of the mesoderm in Drosophila. This genetic cascade ultimately results in the specification of individual cell fates culminating in the formation of the heart. The chapter also describes the role of the known genetic factors that are required for the initial specification and the later differentiation of the heart together with a comparison of the molecular-genetic mechanisms that lead to heart formation in Drosophila with those that may be involved in heart formation in vertebrates.