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C-terminal SARAH domain found in scaffold protein salvador (Sav), Ras-association domain proteins, and mammalian STE20-like protein kinases (MST) The SARAH (Salvador-RassF-Hippo) domain family includes scaffold protein salvador (Sav), Ras-association domain proteins (RASSF1-6), and mammalian STE20-like protein kinase (MST) subfamily members (MST1-2 and Hippo). Sav is a scaffold protein mainly found in metazoans. Drosophila melanogaster Sav, also called Shar-pei (SHRP), promotes both cell cycle exit and apoptosis in Drosophila. It plays a key role in the Hippo/SWH (Sav/Wts/Hpo) signaling pathway. Human protein salvador homolog 1, also called 45 kDa WW domain protein (WW45), acts as a mammalian sterile 20-like kinase 1 (MST1)-binding protein required to enhance MST1-mediated apoptosis. It is a regulator of STK3/MST2 and STK4/MST1 in the Hippo signaling pathway. Classical RASSF proteins interact either directly or indirectly with activated Ras. Ras proteins are small GTPases that are involved in cellular signal transduction. They seem to modulate some of the growth inhibitory responses mediated by Ras and may serve as tumor suppressor genes. RASSF1-6 contains a conserved SARAH motif adjacent to the RA domain that functions in scaffolding and regulatory interactions. MST1/2 and Hippo are involved in a conserved pathway that governs cell contact inhibition, organ size control, and tumor development. MST1 and MST2 are STE20 family stress-activated, pro-apoptotic serine/threonine-protein kinases which, following caspase-cleavage, enter the nucleus and induces chromatin condensation followed by internucleosomal DNA fragmentation. They are key components of the Hippo signaling pathway which plays a pivotal role in organ size control and tumor suppression by restricting proliferation and promoting apoptosis. Hippo (Hpo), also called STE20-like kinase MST (dMST), is the Drosophila homolog of STE20-like protein kinases, MST1 and MST2. It is a STE20 family serine/threonine-protein kinase that functions as a tumor suppressor by restricting cell proliferation and promotes apoptosis in conjunction with salvador and warts. Hpo also plays a key role in the Hippo/SWH signaling pathway. This model corresponds to the C-terminal SARAH domain, a characteristic coiled-coil structure. It is a small helical module that is important in signal-transduction networks. The central function of the SARAH domain seems to be the mediation of homo- and heterodimerization between SARAH domain-containing proteins. |
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Jiyao W et al.(2023). "The conserved domain database in 2023.",