Effects of anti-C23 (nucleolin) antibody on transcription of ribosomal DNA in Chironomus salivary gland cells.
Protein C23 (also called nucleolin or 100-kDa nucleolar protein) is a major nucleolar phosphoprotein involved in ribosome biogenesis. To determine the effects of protein C23 on preribosomal RNA (pre-rRNA) synthesis anti-C23 antiserum was microinjected into nuclei of Chironomus tentans salivary glands. Transcription was measured by incubation of the glands with 32P-labeled RNA precorsors followed by microdissection of nucleoli, RNA extraction, and electrophoretic analyses. Injection of the anti-C23 antibody caused a 2- to 3.5-fold stimulation of 32P incorporation into 38S pre-rRNA. No stimulation was observed in salivary glands injected with preimmune serum or antiserum preabsorbed with protein C23. The stimulatory effect was selective for pre-rRNA as indicated by the lack of stimulation of 32P incorporation into extranucleolar RNA. Injection of the antiserum produced little or no effect on pre-RNA processing as measured by the relative amounts of 32P-labeled intermediate cleavage products of pre-rRNA in stimulated versus control glands. When protein extracts of Chironomus tentans salivary gland nuclei were probed on Western blots with anti-C23 antibody the predominant cross-reacting species was a 110-kDa polypeptide which had an electrophoretic mobility similar to that of protein C23. These results suggest that protein C23 not only is involved in ribosome assembly but also plays a role in regulating the transcription of the preribosomal RNA.
Egyhazi
E
E
Department of Medical Cell Biology, Karolinska Institutet, Stockholm, Sweden.
Pigon
A
A
Chang
J H
JH
Ghaffari
S H
SH
Dreesen
T D
TD
Wellman
S E
SE
Case
S T
ST
Olson
M O
MO
D000818:Animals; D002478:Cells, Cultured; D002683:Chironomidae; D004275:DNA, Ribosomal / Q000235:genetics*; D004591:Electrophoresis, Polyacrylamide Gel; D007106:Immune Sera; D015151:Immunoblotting; D008845:Microinjections; D009687:Nuclear Proteins / Q000276:immunology / Q000502:physiology*; D010750:Phosphoproteins / Q000276:immunology / Q000502:physiology*; D012322:RNA Precursors / Q000096:biosynthesis*; D012335:RNA, Ribosomal / Q000096:biosynthesis*; D016601:RNA-Binding Proteins; D014158:Transcription, Genetic; D000097796:Nucleolin
D004275:DNA, Ribosomal; D007106:Immune Sera; D009687:Nuclear Proteins; D010750:Phosphoproteins; D012322:RNA Precursors; D012335:RNA, Ribosomal; D016601:RNA-Binding Proteins; D000097796:Nucleolin