Sina is a RING-type E3 ubiquitin ligase first identified in Drosophila, a protein essential for the determination of the R7 pathway in photoreceptor cell development [3]. Murine and human homologues of Sina have also been identified, namely Siah1 and ...
Sina is a RING-type E3 ubiquitin ligase first identified in Drosophila, a protein essential for the determination of the R7 pathway in photoreceptor cell development [3]. Murine and human homologues of Sina have also been identified, namely Siah1 and Siah2 [1-4], and also in Arabidopsis, SINAT3 [5]. These proteins have a RING-type zinc finger at the N-terminal followed by two zinc fingers and a C-terminal TRAF-like domain (Pfam:PF03145) [1-5]. This entry represents the central C2H2 zinc finger domains.
The seven in absentia (sina) gene was first identified in Drosophila. The Drosophila Sina protein is essential for the determination of the R7 pathway in photoreceptor cell development: the loss of functional Sina results in the transformation of the ...
The seven in absentia (sina) gene was first identified in Drosophila. The Drosophila Sina protein is essential for the determination of the R7 pathway in photoreceptor cell development: the loss of functional Sina results in the transformation of the R7 precursor cell to a non- neuronal cell type. The Sina protein contains an N-terminal RING finger domain, through which it binds E2 ubiquitin-conjugating enzymes (UbcD1). Sina also interacts with Tramtrack (TTK88) via PHYL. Tramtrack is a transcriptional repressor that blocks photoreceptor determination, while PHYL down-regulates the activity of TTK88. In turn, the activity of PHYL requires the activation of the Sevenless receptor tyrosine kinase, a process essential for R7 determination. It is thought that thus Sina targets TTK88 for degradation, therefore promoting the R7 pathway. Murine and human homologues of Sina have also been identified, namely siah1/2. Siah-1 [1,4,5] also binds E2 enzymes (UbcH5) and through a series of physical interactions, targets beta-catenin for ubiquitin degradation. Siah-1 expression is enhanced by p53, itself promoted by DNA damage. Thus this pathway links DNA damage to beta-catenin degradation [2,3]. Sina proteins, therefore, physically interact with a variety of proteins. Following the RING domain, these proteins have two zinc fingers and a TRAF-like domain, involved in interactions with other proteins. In addition to the Drosophila protein and mammalian homologues, this family also includes homologues from Caenorhabditis elegans and Arabidopsis thaliana [6]. This entry represents the C-terminal TRAF-like domain.
The N terminal domain of Siah interacting protein (SIP) adopts a helical hairpin structure with a hydrophobic core stabilised by a classic knobs-and-holes arrangement of side chains contributed by the two amphipathic helices. Little is known about th ...
The N terminal domain of Siah interacting protein (SIP) adopts a helical hairpin structure with a hydrophobic core stabilised by a classic knobs-and-holes arrangement of side chains contributed by the two amphipathic helices. Little is known about this domain's function, except that it is crucial for interactions with Siah. It has also been hypothesised that SIP can dimerise through this N terminal domain [1].
