Deen Thifeen, Shimizu Hideyuki, Wilkin Marian B, Baron Martin
School of Biological Sciences, Faculty of Biology Medicine and Health, University of Manchester, Oxford Rd., Manchester M13 9PT, UK.
Biomolecules. 2025 Jul 26;15(8):1082. doi: 10.3390/biom15081082.
We identified Murashka, a RING finger protein, in an oogenesis screen as a regulator of ovary germline stem cell niche development. Mutant alleles of exhibited an enlarged niche phenotype reminiscent of increased Notch signalling and displayed genetic interactions with alleles, and with , a regulator of Notch during niche development. These interactions uncovered both positive and negative impacts on Notch in different genetic backgrounds. In S2 cells, Murashka formed a complex with Notch and colocalised with Notch in the secretory pathway. Murashka expression in S2 cells down-regulated Notch signalling levels but could result in increased fold induction due to the proportionally greater decrease in basal ligand-independent activity. In vivo Murashka expression had different outcomes on different Notch target genes. We observed a decrease in the expression of along the anterior/posterior boundary of the wing imaginal disc, but not of at the dorsal/ventral boundary. Instead, weak ectopic was observed, which was synergistically increased by the coexpression of Deltex, a positive regulator of ligand-independent signalling. Our results identify a novel developmental role for , a gene previously only associated with a function in long-term memory, and indicate a regulatory role for Murashka through a physical interaction with Notch that has context-dependent outcomes. Murashka adds to a growing number of ubiquitin ligase regulators which interact with Notch at different locations within its secretory and endocytic trafficking pathways.
我们在卵子发生筛选中鉴定出一种环状结构域蛋白Murashka，它是卵巢生殖系干细胞微环境发育的调节因子。其突变等位基因表现出扩大的微环境表型，让人联想到Notch信号增加，并与相关等位基因以及在微环境发育过程中Notch的调节因子表现出遗传相互作用。这些相互作用揭示了在不同遗传背景下对Notch的正负影响。在S2细胞中，Murashka与Notch形成复合物，并在分泌途径中与Notch共定位。Murashka在S2细胞中的表达下调了Notch信号水平，但由于基础配体非依赖性活性的下降比例更大，可能导致诱导倍数增加。在体内，Murashka的表达对不同的Notch靶基因有不同的影响。我们观察到在翅成虫盘的前后边界处的表达下降，但在背腹边界处的表达没有下降。相反，观察到微弱的异位表达，通过共表达配体非依赖性信号的正向调节因子Deltex，这种异位表达协同增加。我们的结果确定了一个以前仅与长期记忆功能相关的基因的新的发育作用，并表明Murashka通过与Notch的物理相互作用发挥调节作用，这种作用具有背景依赖性结果。Murashka增加了越来越多的泛素连接酶调节因子的数量，这些调节因子在Notch的分泌和内吞运输途径中的不同位置与Notch相互作用。
