Direct differential absorbance profiles of denaturing transitions in ribosomal and mRNA

Reiteration frequency of procollagen genes in the guinea pig genome. Collagen genes are not amplified during granuloma fibroblasts differentiation

Procollagen mRNA was purified from collagen synthesizing polysomes obtained from an experimental guinea pig granuloma, and iodinated in vitro. The procollagen 125I-labelled mRNA was hibridized with granuloma and liver guinea pig DNA in vast DNA excess conditions. A Cot 1/2 800-900 mol . s . 1-1 for both tissues was obtained from the hybridization curves. With these results, we could suggest the existence of 11-13 procollagen genes per haploid genome. By the analysis of the hybridization data it was possible to infer that there is no genomic amplification in tissues highly specialized in the synthesis of collagen such as granuloma.

Secondary structure of mouse and rabbit alpha- and beta-globin mRNAs: differential accessibility of alpha and beta initiator AUG codons towards nucleases

The nucleotide sequence from the 5' terminus inward of one third of mouse alpha- and beta maj-globin messenger RNAs has been established. In addition, using 5' 32P end-labeled mRNAs as substrates and S1 and T1 nucleases as probes for single-stranded regions, the secondary structures of mouse and rabbit alpha- and beta-globin mRNAs have been analyzed. Our results indicate that the AUG initiator codon in both mouse and rabbit beta-globin mRNA is quite susceptible to cleavage with S1 and T1 nucleases, suggesting that it resides in a single-stranded exposed region. In contrast, the initiator AUG in the alpha-globin mRNA of both species is inaccessible to cleavage, indicating that it is either buried by tertiary structure or is base-paired. Since the rate of initiation of protein synthesis with beta-globin mRNA in rabbit reticulocyte is 30--40% faster than for alpha-globin mRNA, these results imply a possible correlation between the differential rates of initiation with these two mRNAs and the accessibility of the respective AUG initiator codons.