Chromatin Lipid Microdomains

In cell nucleus, polar and neutral lipids are responsible for the nuclear membrane and nuclear matrix fluidity. In specif- ic sections of inner nuclear membranes that bind the active chromatin, lipid microdomains that constitute a platform for the transcription process are present. Nuclear lipid microdomains appear as a homogenous pop- ulation of closed, spherical or ovoid vesicle-like structures composed by an exact ratio of phosphatidylcholine, sphin- gomyelin and cholesterol. This ratio is maintained by neutral sphingomyelinase, sphingomyelin-synthase and reverse sphingomyelin-synthase activity. Interestingly, exist two pools of cholesterol in the chromatin: one called “sphingo- myelin-free cholesterol fraction” and another “sphingomy- elin-linked cholesterol fraction”. The latest fraction is regu- lated by neutral sphingomyelinase and sphingomyelin-syn- thase activity. The organization of sphingomyelin-linked cholesterol fraction in chromatin microdomains is reported in this commentary.