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[Changes in the RNA-dependent DNA-polymerase activity of retrovirus-like particles in the rat liver during postnatal
Insights
RNA-dependent DNA-polymerase activity, a key enzyme in reverse transcription, is significantly higher in newborn rat liver microsomes. This suggests retroviral activity may play a role in early development.
Area of Science:
- Biochemistry
- Molecular Biology
- Developmental Biology
Background:
- RNA-dependent DNA-polymerase activity is crucial for reverse transcription.
- Retroviruses utilize reverse transcriptase to integrate genetic material.
- Understanding age-related changes in enzyme activity is important for developmental studies.
Purpose of the Study:
- To investigate RNA-dependent DNA-polymerase activity in rat liver fractions across different age groups.
- To characterize retroviral particles in rat liver and their potential role in development.
Main Methods:
- Isolation and fractionation of rat liver tissue (postmicrosomal and microsomal fractions).
- Assay of RNA-dependent DNA-polymerase activity.
- Density gradient centrifugation to isolate particles.
- Enzymatic assays (RNAse sensitivity) and morphological analysis.
Main Results:
- Microsomal RNA-dependent DNA-polymerase activity was ~10-fold higher in 4-6 day old rats compared to adults.
- Postmicrosomal activity was 30-35% higher in 3-day old rats.
- Retrovirus-like particles were identified in the microsomal sediment of all age groups.
- Enzyme activity showed sensitivity to RNAse and presence of reverse transcriptase.
Conclusions:
- Elevated reverse transcription in early postnatal rat liver may be linked to ongoing cell differentiation and enzymatic imprinting.
- Retrovirus-like particles are present in rat liver and their activity varies with age.
- The findings suggest a potential role for reverse transcription in early mammalian development.
Abstract:
The RNA-dependent DNA-polymerase activity was studied in the postmicrosomal fraction and in the microsomal sediment of the liver of the newborn and adult Wistar rats. In the microsomal sediment of 4-6 day old rats the RNA-dependent DNA-polymerase activity was approximately by one order of magnitude higher than in that of 2 week old and adult rats. In the postmicrosomal fraction of 3 day old rats the RNA-dependent DNA-polymerase activity was also higher, but only by 30-35%, than in that of animals of the other age groups. Particles with density of 1.17 g/ml were found in the microsomal sediment of all studied animals. The characteristic morphology, sensitivity of the particle RNA-dependent DNA-polymerase activity to RNAse and the presence of reverse transcriptase allow for these particles to be referred to as retroviruses. A suggestion is put forward that the high intensity of reverse transcription during the early postnatal period can be due to still continuing processes of cell differentiation and enzymatic imprinting.