髓系白血病因子 1 (Mlf1) 被确定为一种影响人类造血分化的原癌蛋白。然而，其细胞功能仍然难以捉摸，涵盖从细胞周期调节到调节蛋白质聚集体形成和参与纤毛发生的作用。鉴于在真核生命树中可以找到 Mlf1 结构保守的同源物，我们决定表征其在这种表型多效性背后的细胞作用。使用单细胞真核生物肠贾第鞭毛虫模型，我们证明其 Mlf1 同源物 (GiMlf) 主要定位于两种类型的胞质灶：微管结构，在其中与 Hsp40 相互作用，以及富含泛素的无膜区室，发现于线粒体附近。称为线粒体的相关细胞器，含有 26S 蛋白酶体调节亚基 4。在细胞应激时，GiMlf 要么重新定位到受影响的区室，要么分散在细胞质中，随后在恢复阶段累积成扩大的病灶。体外测定表明，GiMlf 可以通过其对信号磷脂的亲和力被招募到膜上。重要的是，gimlf 敲除菌株中的胞质灶减少，其表现出广泛的蛋白质组变化，表明蛋白质稳态受损。与其他细胞系统的数据一致，我们认为 Mlf 通过介导蛋白质折叠和降解的功能特异性焦点的形成来响应蛋白毒性应激。版权所有：© 2024 Vinopalová 等人。这是一篇根据知识共享署名许可条款分发的开放获取文章，允许在任何媒体上不受限制地使用、分发和复制，前提是注明原始作者和来源。

Myeloid leukemia factor 1 (Mlf1) was identified as a proto-oncoprotein that affects hematopoietic differentiation in humans. However, its cellular function remains elusive, spanning roles from cell cycle regulation to modulation of protein aggregate formation and participation in ciliogenesis. Given that structurally conserved homologs of Mlf1 can be found across the eukaryotic tree of life, we decided to characterize its cellular role underlying this phenotypic pleiotropy. Using a model of the unicellular eukaryote Giardia intestinalis, we demonstrate that its Mlf1 homolog (GiMlf) mainly localizes to two types of cytosolic foci: microtubular structures, where it interacts with Hsp40, and ubiquitin-rich, membraneless compartments, found adjacent to mitochondrion-related organelles known as mitosomes, containing the 26S proteasome regulatory subunit 4. Upon cellular stress, GiMlf either relocates to the affected compartment or disperses across the cytoplasm, subsequently accumulating into enlarged foci during the recovery phase. In vitro assays suggest that GiMlf can be recruited to membranes through its affinity for signaling phospholipids. Importantly, cytosolic foci diminish in the gimlf knockout strain, which exhibits extensive proteomic changes indicative of compromised proteostasis. Consistent with data from other cellular systems, we propose that Mlf acts in the response to proteotoxic stress by mediating the formation of function-specific foci for protein folding and degradation.Copyright: © 2024 Vinopalová et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.