In situ localization of cAMP-dependent protein kinases in nuclear and chromosomal substructures: relation to transcriptional activity.
Catalytic (C) and regulatory subunits (RI, RII) of cAMP-dependent protein kinase (PKA) were localized in cell nuclei of various rat tissues by immunogold electron microscopy. A specific labeling within the interchromatin space was found to be associated with perichromatin fibrils, interchromatin granules, and coiled bodies. Condensed chromatin and perichromatin granules were not labeled. In the nucleolus, most gold particles were found in the dense fibrillar component. Quantitation of labeling densities for the C-subunit from cells at different stages of spermatogenesis indicated that the nuclear concentration of PKA varies inversely with the amount of condensed chromatin. No parallel alterations in C-immunoreactivities were observed in the cytoplasm. Immunofluorescence studies on polytene chromosomes of Chironomus thummi with a confocal laser scanning microscope showed a significantly more intense labeling of the C-subunit in transcriptionally active sites (puffs) as compared to inactive bands. Our results indicate that local concentrations of PKA in the nucleus have physiological significance in the control of gene activity. In addition, they suggest that PKA plays a regulatory role also in RNA processing.
Trinczek
B
B
Clinical Biochemistry, University of Göttingen, Germany.
Robert-Nicoud
M
M
Schwoch
G
G
D000818:Animals; D002466:Cell Nucleolus / Q000201:enzymology* / Q000648:ultrastructure; D002683:Chironomidae; D002843:Chromatin / Q000737:chemistry* / Q000648:ultrastructure; D007150:Immunohistochemistry; D008297:Male; D011494:Protein Kinases / Q000032:analysis*; D051381:Rats; D017208:Rats, Wistar; D012469:Salivary Glands / Q000201:enzymology / Q000648:ultrastructure; D013091:Spermatogenesis; D013094:Spermatozoa / Q000201:enzymology / Q000648:ultrastructure; D014158:Transcription, Genetic
D002843:Chromatin; D011494:Protein Kinases