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Nuclear actin network assembly by formins regulates the SRF coactivator MAL
Christian Baarlink1, Haicui Wang, Robert Grosse
1Institute of Pharmacology, Biochemical-Pharmacological Center, University of Marburg, Germany.
Formins build actin filaments in the nucleus, activating serum response factor (SRF) transcriptional activity. This nuclear actin assembly, driven by formins like mDia, is key to the cell's serum response.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Formins are known cytoplasmic activators of actin filament assembly.
- Cytoplasmic actin polymerization influences the release of megakaryocytic acute leukemia (MAL) protein, impacting serum response factor (SRF) transcriptional activity.
Purpose of the Study:
- To investigate the role of formins in nuclear actin polymerization and its effect on MAL-SRF transcriptional activity.
- To determine if nuclear actin assembly is involved in the serum response pathway.
Main Methods:
- Utilized an optogenetic tool to control the activity of the endogenous formin mDia within the nucleus.
- Observed actin filament assembly, MAL nuclear accumulation, and SRF activity in response to serum stimulation and formin activation.
Main Results:
- Formins were found to polymerize actin filaments within the mammalian nucleus in a serum-dependent manner.
- Optogenetic activation of nuclear mDia led to rapid actin network assembly, MAL nuclear translocation, and enhanced SRF activity.
- The nuclear actin assembly was reversible and directly linked to SRF transcriptional activity.
Conclusions:
- A dynamic actin polymer network exists within the nucleus and plays a crucial role in mediating the serum response.
- Formins act as key regulators of nuclear actin dynamics, influencing transcriptional activity through the MAL-SRF pathway.
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