Inserts within the mRNA sequence on the 15 S globin mRNA precursor from chicken

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Chicken immature red blood cells possess nuclear RNA with globin sequences.
• Two RNA species, 9S and 15S, contain globin coding sequences, with 15S likely being the precursor to 9S globin mRNA.

Purpose of the Study:

• To investigate if the globin mRNA sequence within the 15S precursor RNA is interrupted by interspersed sequences.
• To determine the structure of the globin mRNA precursor in chicken red blood cells.

Main Methods:

• Hybridization of radiolabeled nuclear 15S RNA with excess unlabeled globin complementary DNA (cDNA).
• Degradation of non-hybridized RNA using RNase A, followed by proteinase K treatment and phenol extraction.
• Melting of cDNA-RNA hybrids and degradation of cDNA using DNase I.
• Separation of cDNA-protected RNA fragments via polyacrylamide gel electrophoresis in formamide.

Main Results:

• Analysis of 15S RNA revealed three RNA fragments (approx. 320, 200, and 120 nucleotides) after processing.
• Analysis of 9S RNA yielded a single fragment (650-700 nucleotides).
• The presence of multiple fragments from 15S RNA indicates interruptions within the globin mRNA sequence.

Conclusions:

• The 15S globin mRNA precursor in chicken red blood cells contains at least two inserts within the mRNA sequence.
• These inserts suggest that the globin gene in chickens is transcribed from a gene with intervening sequences (introns).
• This finding provides evidence for the existence of split genes in eukaryotes.