Deficient transcription of subunit RPA 40 of RNA polymerase I and III in heart of rats with neonatal asphyxia.
RNA polymerases transcribe nuclear genes for ribosomal RNA thus representing ribosomal biogenesis. RNA polymerase I transcribes class I genes, coding for large ribosomal RNA and is located in the nucleolus. RNA polymerase III transcribes class III genes, those that encode a number of small ribosomal RNA molecules. Both RNA polymerases form ribosomal biogenesis in a concerted action and have a common subunit, RPA40, essential for function and integrity. The aim of our study was to study the influence of hypoxia/asphyxia on transcription of this subunit as deterioration of ribosomal biogenesis may not be compatible with life. To test this hypothesis we used a nonsophisticated model of neonatal asphyxia. Rat pups were exposed to various asphyctic periods up to twenty minutes and heart tissue was taken for the evaluation of mRNA RPA40 levels, pH measurements and histological evaluation of the nucleolus by silver staining. mRNA RPA40 levels gradually decreased with the length of the asphyctic period paralleling the decrease of pH. Silver staining was remarkably decreased at the asphyctic period of 20 minutes. Our findings of decreased transcription of this essential RNA polymerase subunit indicate impairment of the ribosomal RNA synthetizing machinery and the histological findings suggest its structural relevance. This is the first in vivo observation of deteriorated RNA polymerase in asphyxia/hypoxia.
Hoeger
H
H
University of Vienna, Dpt of Pediatrics, Austria.
Labudova
O
O
Mosgoeller
W
W
Herrera-Marschitz
M
M
Fuerst
G
G
Kitzmüller
E
E
Lubec
B
B
D000199:Actins / Q000378:metabolism; D000818:Animals; D001238:Asphyxia Neonatorum / Q000201:enzymology* / Q000235:genetics; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007231:Infant, Newborn; D009206:Myocardium / Q000201:enzymology* / Q000473:pathology; D011247:Pregnancy; D012318:RNA Polymerase I / Q000172:deficiency* / Q000235:genetics; D012320:RNA Polymerase III / Q000172:deficiency* / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014158:Transcription, Genetic
D000199:Actins; D012333:RNA, Messenger; D012318:RNA Polymerase I; D012320:RNA Polymerase III