RNA synthesis in permeable mouse ascites sarcoma cells

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Studying RNA synthesis requires methods that preserve cellular integrity and enzyme activity.
• Isolated nuclei can exhibit altered RNA polymerase activity compared to the in vivo state.
• Accurate assessment of distinct RNA polymerase activities (I, II, III) is crucial for understanding gene regulation.

Purpose of the Study:

• To establish a permeable cell system for studying endogenous RNA synthesis.
• To differentiate and quantify the activities of RNA polymerases I, II, and III in situ.
• To compare RNA synthesis in permeable cells with that in isolated nuclei.

Main Methods:

• Mouse ascites sarcoma cells were rendered permeable using a hypotonic buffer treatment.
• Permeability was achieved for nucleoside triphosphates and alpha-amanitin.
• Differential sensitivity of RNA polymerases I, II, and III to alpha-amanitin was exploited for separate activity determinations.

Main Results:

• The permeable cell system allowed for the distinct measurement of RNA polymerase I, II, and III activities.
• RNA polymerase II activity in permeable cells was significantly higher relative to total RNA synthesis compared to isolated nuclei.
• The ratio of RNA polymerase II to total RNA synthesis in isolated nuclei was found to be disproportionately low, likely due to altered enzyme activity.

Conclusions:

• The permeable cell system provides a more accurate representation of in vivo RNA synthesis than isolated nuclei.
• This system is valuable for studying the specific activities of RNA polymerases I, II, and III in their native cellular environment.
• The findings highlight the utility of permeable cells for investigating transcriptional regulation and RNA production.