Identification of precursor molecules to individual tRNA species from Bombyx mori.

Abstract
Short-labeled 4.5S RNA molecules isolated from the posterior silk gland of B. mori can be separated by 2-dimensional polyacrylamide gel electrophoresis into many discrete species, some of which are radiochemically pure by the criteria of RNA fingerprinting. One region of the gel contains 2 precursor RNA, one to each of the known alanine transfer RNA. Each precursor tRNAAla molecule contains all of the internal oligonucleotides present in the corresponding tRNAAla species plus new 5''- and 3''-terminal sequences. Precursor molecules to .**GRAPHIC**. (which differ from each other in size) are contained in 2 other gel regions, and a 4th region contains a precursor to .**GRAPHIC**. Both transcription initiator purine tetraphosphate nucleosides are present in unfractionated tRNA precursor mixtures, with pppA- predominating over pppG-. Minor nucleotides are present in B. mori tRNA precursors. No polycistronic tRNA gene transcripts were observed.