biostudies-literaturePimm MLNational Institutes of HealthNIH HHSNIGMS NIH HHSe202305065https://www.ebi.ac.uk/biostudies/studies/S-EPMC11117073biostudies-literatureUnknown223(9)Cell processes require precise regulation of actin polymerization that is mediated by plus-end regulatory proteins. Detailed mechanisms that explain plus-end dynamics involve regulators with opposing roles, including factors that enhance assembly, e.g., the formin mDia1, and others that stop growth (capping protein, CP). We explore IQGAP1's roles in regulating actin filament plus-ends and the consequences of perturbing its activity in cells. We confirm that IQGAP1 pauses elongation and interacts with plus ends through two residues (C756 and C781). We directly visualize the dynamic interplay between IQGAP1 and mDia1, revealing that IQGAP1 displaces the formin to influence actin assembly. Using four-color TIRF, we show that IQGAP1's displacement activity extends to formin-CP "decision compleThe Journal of cell biologyCoordination of actin plus-end dynamics by IQGAP1, formin, and capping protein.PMC11117073GM133485R35 GM133485Nobles ADHaney LMHenty-Ridilla JLPimm MLHaarer BKMarcin AGAlcaide Eligio MfalseCoordination of actin plus-end dynamics by IQGAP1, formin, and capping protein.Cell processes require precise regulation of actin polymerization that is mediated by plus-end regulatory proteins. Detailed mechanisms that explain plus-end dynamics involve regulators with opposing roles, including factors that enhance assembly, e.g., the formin mDia1, and others that stop growth (capping protein, CP). We explore IQGAP1's roles in regulating actin filament plus-ends and the consequences of perturbing its activity in cells. We confirm that IQGAP1 pauses elongation and interacts with plus ends through two residues (C756 and C781). We directly visualize the dynamic interplay between IQGAP1 and mDia1, revealing that IQGAP1 displaces the formin to influence actin assembly. Using four-color TIRF, we show that IQGAP1's displacement activity extends to formin-CP "decision comple2024-01-01T00:00:00Z2024 Sep2026-06-03T06:51:25.895Z2026-04-25T03:22:13.046ZS-EPMC111170733878734910.1083/jcb.202305065