title: [Is the regulation of the expression of MMTV proviruses in various cell types linked to glucocorticoid receptors and/or the structure of chromatin?].
abstract: The expression of the mouse mammary tumor virus (MMTV) was studied in undifferentiated embryonal carcinoma cells (EC), in partially differentiated myoblasts derived from EC cells and in fully differentiated myotubes. Whereas no MMTV RNA could be detected in EC cells, relatively large amounts of tumor virus RNA were found in myoblasts. The MMTV RNA level was reduced in myotubes derived from myoblastic differenciation. DNaseI sensibility of MMTV DNA in chromatin allows us to show conformational changes in EC cell myoblasts and GR mammary cell chromatin which could be associated with MMTV RNA synthesis. The glucocorticoid hormones dexamethasone which stimulates the MMTV RNA synthesis in differentiated mammary cells did not affect this synthesis in myoblasts. By contrast, the reduced synthesis of MMTV RNA in myotubes was overcome with dexamethasone. The differential MMTV RNA synthesis is not related to different amount of receptor and its hormonal regulation is not associated with a conformational change of chromatin.
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D002843:Chromatin / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology; D005786:Gene Expression Regulation; D008324:Mammary Tumor Virus, Mouse / Q000235:genetics*; D051379:Mice; D011487:Protein Conformation; D011965:Receptors, Glucocorticoid / Q000502:physiology*; D011987:Receptors, Steroid / Q000502:physiology*
chemical_list: D002843:Chromatin; D011965:Receptors, Glucocorticoid; D011987:Receptors, Steroid; D003907:Dexamethasone
vernacular_title: La régulation de l'expression des provirus MMTV dans différents types cellulaires est-elle liée aux récepteurs des glucocorticoïdes et/ou à la structure de la chromatine?