L. Davis et al., REVERSIBLE DISASSEMBLY OF TRANSCRIPTION DOMAINS IN LYMPHOCYTE NUCLEI DURING INHIBITION OF RNA-SYNTHESIS BY DRB, Biology of the cell, 78(3), 1993, pp. 163-180
We are investigating the roles of RNA synthesis, chromatin structure a
nd nuclear matrix organization in establishing and maintaining transcr
iption domains, using mitogen stimulated lymphocytes as a model system
. In a continuing study, the effects of the RNA polymerase inhibitor D
RB and of its removal on nuclear organization have been examined by EM
cytochemistry and by immunofluorescence labelling of the nuclear matr
ix PI1, Sm and nucleolar fibrillarin antigens. Chromatin, interchromat
in granules and nucleoli were extensively restructured after DRB, as w
ere matrix antigens. According to cytochemical staining properties, th
e conformation of DRB-induced condensed chromatin resembled that in pa
rtially stimulated lymphocytes. The nucleoplasmic fibrogranular RNP ne
twork appeared little altered, but the fibrillar proteinaceous interch
romatinic regions, interpreted as representing the nuclear matrix in s
itu, were more affected. After removal of DRB, nuclei recovered the or
ganization and transcriptional activity of controls within 8 h. These
results suggest that the matrix subtending transcription domains remai
ns stable when transcription is arrested, even though the chromatin an
d individual RNP components of the domains are disorganized. The data
further indicate that absence of transcription is not solely accountab
le for the highly aggregated state of the chromatin in resting lymphoc
ytes.