Effect of Gestational Age on RNA Polymerase Activity in the Fetal Guinea Pig Brain. 255

The present study investigates maturational changes of RNA polymerase activity in the fetal guinea pig. RNA polymerase II transcribes mRNA, type I rRNA, and type III tRNA. Total, bound and free RNA polymerase activity was determined in brain cell nuclei isolated from fetal guinea pigs at 40, 50, and 60 days(term). RNA polymerase activity was determined in 50 mM TrisHCl buffer(pH 8.3), 25 mM (NH₄)₂SO₄, 3 mM MnCl₂, 2mM MgCl₂, 0.3 mM ATP, 0.3 mM GTP, 0.3 mM CTP and 1μ M 3HUTP. PolydAdT was used to measure free RNA polymerase activity and Bound RNA polymerase was determined as actinomycinD sensitive activity and RNA polymerase II asμamanitin sensitive activity. RNA polymerase activity was expressed as fmole ³HUTP incorporated/ mg protein/hour.Table

Table 1

Bound RNA polymerase I & III was 31.7% at 40 days and 37.0% at 60 days(p=NS). However, bound RNA polymerase II decreased from 22.7% at 40 days to 12.8% at 60 days (p<0.05). The results show that RNA polymerase, I, II, and III activity in the fetal guinea pig brain increases with advancing gestational age from 40 to 60 days gestation. The proportion of RNA polymerase I and III bound to DNA remains constant during this period, but a greater proportion of RNA polymerase II is DNA bound in the preterm than in the term fetal brain.

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