Differential immunoreactivity for Z-DNA in rat myoblast nuclei during their terminal differentiation.
L6 myoblasts in vitro accomplish the process of terminal differentiation from dividing mononucleated cells to quiescent plurinucleated myotubes, synthesizing muscle-specific proteins. They have been tested, using paraformaldehyde and acetic acid fixations and immunocytochemical techniques, for the presence of Z-DNA at different stages: namely after 3, 5 and 8-9 days of culture. The nuclei of the actively dividing 3-day myoblasts were strongly Z-DNA and B-DNA-positive. The inhibition of replication by araC did not diminish the reaction. In the myotubes, the nuclei became Z-DNA-negative but were still B-DNA-positive. In contrast, the nuclei of a non-fusing alpha-amanitin-resistant mutant (Ama102) stayed Z-DNA-positive. These results tend to show that during the process of terminal differentiation Z-DNA either becomes less accessible or is present in undetectable amounts. In circular DNAs, it has been shown that the presence of Z-DNA depends on their negative supercoiling. In addition, the presence of closed superhelical loops of nuclear DNA has been demonstrated in several mammalian cell types; moreover, the density of DNA topological turns in these loops varies during cellular differentiation and malignant transformation. The relationship between these results and ours is discussed.
Briane
D
D
Delain
D
D
Sénéchal
H
H
Taillandier
E
E
Wahrmann
J P
JP
Hervé
B
B
D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003561:Cytarabine / Q000494:pharmacology; D004247:DNA / Q000276:immunology / Q000378:metabolism*; D005404:Fixatives; D007158:Immunologic Techniques; D009132:Muscles / Q000166:cytology*; D051381:Rats
D005404:Fixatives; D003561:Cytarabine; D004247:DNA