Multilayered control of mRNA delivery to cell protrusions drives localized mini-cytoplasm establishment for stress-induced cell activation

In response to stress, cells exploit plasticity to self-activate and form protrusions that explore the environment and guide migration. While protrusion initiation is well characterized, their maturation and functional composition remain poorly understood. Here, using a new pooled genetic approach (ReGenT-seq) to interrogate chromatin factors controlling epidermal progenitor activation, we unexpectedly identified Cbx3 as a critical determinant of protrusion formation. Beyond its nuclear activities, we revealed a cytoplasmic moonlighting function of CBX3 that governs the subcellular localization of specific mRNAs within polarizing protrusions of migrating epidermal progenitor cells, as well as in invadopodia of squamous carcinoma cells. CBX3-dependent mRNA transport promotes the localized establishment of multiple organelles, including the endoplasmic reticulum and lysosomes, within maturing protrusions, and regulates focal adhesion dynamics. Together, our findings uncover a multilayered gene regulatory mechanism controlling cell motility through protrusionogenesis and identify a chromatin-to-cell-protrusion mRNA transport pathway that represents a potential therapeutic target for enhancing wound healing and limiting cancer invasion. Here the authors show that, under stress, epithelial cells reveal an unexpected role for a chromatin factor in directing mRNA to cell protrusions, enabling local organelle assembly and cell movement, with implications for wound healing and cancer invasion.