Organization of the thyroid hormone receptor in the chromatin of C6 glial cells: evidence that changes in receptor levels are not associated with changes in receptor distribution.
The association of [125I]T3-receptor complexes with C6 cell chromatin was analyzed after a limited digestion with micrococcal nuclease (MN) or DNase I. Both nucleases solubilized up to 60-70% of receptor and 0.4 M KCl extracted 70% of the non-digested receptor, thus showing that only a residual fraction of receptor is associated with the nuclear matrix. With DNase I the receptor was released 2-3-fold faster than the bulk of chromatin, whereas a preferential release of receptor over total chromatin was not observed with MN. The digestion of receptor with DNase I and MN occurred 14- and 6-fold faster, respectively, than the appearance of PCA-soluble chromatin. Preincubation for 48 h with 4 nM T3 of 2 mM butyrate significantly altered receptor levels but did not change sensitivity to the nucleases. These results suggest that the thyroid hormone receptor is associated with chromatin highly sensitive to nuclease digestion, and that changes in receptor number are not associated with changes in its distribution in chromatin.
Ortiz-Caro
J
J
Instituto de Investigaciones Biomedicas, CSIC, Facultad de Medicina, Universidad Autonoma de Madrid, Spain.
Yusta
B
B
Pascual
A
A
Aranda
A
A
D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism*; D007700:Kinetics; D009457:Neuroglia / Q000378:metabolism; D009474:Neurons / Q000378:metabolism*; D011988:Receptors, Thyroid Hormone / Q000378:metabolism*
D002843:Chromatin; D011988:Receptors, Thyroid Hormone