Increased levels of glycine tRNA associated with collagen synthesis

Analysis of codon usage for chick Type I collagen indicates that 89% of glycine codons are GGU/C. Since collagens are one-third glycine, chick Type I collagen synthesis should require large amounts of tRNAGly with the anticodon GCC. Earlier chromatographic studies of chick tRNA had indicated that connective tissues showed altered tRNAGly isoacceptor profiles [P. J. Christner and J. Rosenbloom (1976) Arch. Biochem. Biophys. 172, 399-409; H. J. Drabkin and L. N. Lukens (1978) J. Biol. Chem. 253, 6233-6241]. We have therefore used both two-dimensional gel electrophoresis and hybridization analysis to investigate whether collagen synthesis in chick connective tissues is associated with expression of a novel tRNAGly. Liver and calvaria tRNAs produced qualitatively similar patterns when separated on 2-D gels. Northern blots of 2-D-separated tRNAs from liver and calvaria, when hybridized to genes for vertebrate tRNAGly isoacceptors with GCC or UCC anticodons, showed hybridization to the same tRNAs in both tissues. Quantitation of tRNA species by dot blot hybridization indicated an increase in levels of the tRNAGly isoacceptor with anticodon GCC. Tissues synthesizing Type I collagen had a two- to threefold increase in this tRNA while tissues synthesizing Type II collagen showed a more modest increase. We conclude that elevated tRNAGly levels associated with collagen synthesis are due to increased amounts of the same isoacceptor which is the major tRNAGly in other tissues.