Intranuclear actin bundles induced by dimethyl sulfoxide in interphase nucleus of Dictyostelium

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• The cellular slime mold Dictyostelium serves as a model organism for studying eukaryotic cell functions.
• Intranuclear structures and their roles in cellular processes are not fully understood.
• The contractile protein actin is primarily known for its role in the cytoplasm.

Purpose of the Study:

• To investigate the effect of dimethyl sulfoxide (DMSO) on the cellular slime mold nucleus.
• To identify the composition and structure of DMSO-induced intranuclear microfilament bundles.
• To explore the potential nuclear functions of actin.

Main Methods:

• Electron microscopy was used to visualize intranuclear structures.
• Glycerinated cell studies with heavy meromyosin binding assays were performed.
• Mg-adenosine triphosphate was used to assess binding reversibility.

Main Results:

• Dimethyl sulfoxide (DMSO) induces the formation of giant intranuclear microfilament bundles (approx. 3 µm long, 0.85 µm wide) in Dictyostelium.
• These bundles are composed of 6 nm diameter microfilaments that bind heavy meromyosin, confirming they are actin.
• The binding of actin to heavy meromyosin was reversible with Mg-adenosine triphosphate.

Conclusions:

• Intranuclear microfilaments in Dictyostelium are composed of the contractile protein actin.
• Dimethyl sulfoxide (DMSO) directly affects intranuclear actin, leading to the formation of large bundles.
• Nuclear actin likely plays essential roles within the cell nucleus, potentially in nuclear structure or function.