RT Journal Article SR Electronic T1 IntAct: a non-disruptive internal tagging strategy to study actin isoform organization and function JF bioRxiv FD Cold Spring Harbor Laboratory SP 2021.10.25.465733 DO 10.1101/2021.10.25.465733 A1 M.C. van Zwam A1 W. Bosman A1 W. van Straaten A1 S. Weijers A1 E. Seta A1 B. Joosten A1 K. van den Dries YR 2022 UL http://biorxiv.org/content/early/2022/06/09/2021.10.25.465733.abstract AB Actin plays a central role in many cell biological processes including division and motility. Mammals have six, highly conserved actin isoforms with nonredundant biological functions, yet the molecular basis of isoform specificity remains elusive due to a lack of tools. Here, we describe the development of IntAct, an internal tagging strategy to study actin isoform function in fixed and living cells. We first identified a residue pair in β-actin that permits non-disruptive tag integration. Next, we used knock-in cell lines to demonstrate that the expression and filament incorporation of IntAct β-actin is indistinguishable from wildtype. Also, IntAct β-actin remains associated with the actin-binding proteins profilin and cofilin and can be targeted in living cells. To demonstrate isoform-specificity, we generated IntAct γ-actin cells and demonstrate that characteristic actin isoform localization remains unaltered. Together, our data demonstrate that IntAct is a versatile tool to study actin isoform localization, dynamics and molecular interactions.Competing Interest StatementThe authors have declared no competing interest.