Polyadenylated RNA complementary to repetitive DNA in mouse L-cells

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Polyadenylated RNA plays crucial roles in gene expression.
• Understanding the relationship between RNA and DNA sequences is fundamental to molecular biology.

Purpose of the Study:

• To investigate the DNA sequence origins of abundant polyadenylated RNAs in L-cells.
• To determine if frequent RNAs are transcribed from unique or repetitive DNA sequences.

Main Methods:

• Synthesis of complementary DNA (cDNA) using L-cell polyadenylated RNA as a template.
• Renaturation kinetics of cDNA with L-cell DNA to analyze sequence complexity.
• Fractionation of cDNA based on hybridization with polyadenylated RNA to isolate complements of frequent RNAs.
• Density labeling of cDNA with bromodeoxyuridine and fractionation via alkaline Cs2SO4 gradient centrifugation.

Main Results:

• Approximately 70% of synthesized cDNA renatured with L-cell DNA.
• cDNA showed complementarity to unique DNA sequences (30%) and repetitive DNA sequences (10% and 30% corresponding to 20- and 500-fold repetition).
• Fractionated cDNA, enriched in complements of frequent RNAs, hybridized preferentially to repetitive DNA sequences.
• Density-labeled cDNA fractions enriched in repetitive DNA sequences hybridized to frequent polyadenylated RNA.

Conclusions:

• The most frequent polyadenylated RNAs in L-cells are predominantly transcribed from repetitive DNA sequences.
• This suggests a significant role for repetitive DNA elements in the production of abundant RNA transcripts.
• The study provides insights into the transcriptional organization and regulation of the L-cell genome.