Cell fractionation is a method that separates subcellular components and organelles, so that the structures, functions, and molecular compositions of isolated components may be studied. The process starts by homogenizing tissue in a buffered isotonic solution. Homogenization may involve the use of a blender, Dounce homogenizer, or mortar and pestle. The cell homogenate is centrifuged to separate cellular components by their different densities.

Students in the SU Cell Biology laboratory course use cell fractionation to separate subcellular fractions of liver or spinach cells. They analyze these fractions using a Bradford assay to determine protein concentration, SDS-PAGE to separate proteins by mass, and an enzyme assay to determine succinate dehydrogenase activity.

Cell fractionation is a useful tool in cell biology because it allows for the study of cellular components and processes in isolation from the complex network of reactions that occur in a living cell. In a recent study, cell fractionation was used to study the host cell localization of a SARS-CoV-2 protein, Orf8, which is theorized to act as a histone mimic. Certain viruses may employ histone mimicry to affect their host cells’ epigenetic regulation of gene expression to disrupt host responses to infection.

Histone structure, epigenetic modifications, and gene regulation are among the many fascinating topics covered in the SU Cell Biology lecture course.