Interaction of polyribonucleotides with nuclear and chloroplastic DNA of Chlorella pyrenoidosa

Abstract

1. The interaction of various polyribonucleotides with denatured chloroplastic and nuclear DNAs of Chlorella pyrenoidosa has been investigated. 2. Poly(U) and, to a lesser extent, poly(G) and poly(I,G) bind to the denatured chloroplastic DNA, whereas no interaction is detected with poly(A) and poly(C). 3. Poly(G) and poly(I,G) interact with denatured nuclear DNA. Poly(C) binds also, but only at acidic pH. Neither poly(A) nor poly(U) appear to form complexes. 4. Sheared nuclear and chloroplastic DNAs interact with poly(I,G) to give asymmetrical broad peaks slightly displaced towards greater densities in the CsCl gradient. 5. One may conclude that chloroplastic DNA contains dA · T-rich clusters and to a lesser extent dC · G-rich clusters, whereas nuclear DNA contains dC · dG-rich clusters but no detectable amount of dA · dT-rich clusters. Lack of DNA strands separation after interaction of polyribonucleotides suggests that the clusters enriched in one nucleotide are equally distributed between the two strands.