Nirmal K. Das

The role of ribonucleoproteins in the production of mitotic abnormalities

SummaryImmersion of growing roots of onion and lily in aerated solutions of ribonuclease affected their pattern of growth and altered the structure and mitotic distribution of the chromosomes. Action of the enzyme on meristematic cells caused enlargement of nucleoli, excessive contraction, stickiness, adhesion, and clumping of chromosomes, and production of aneuploid and polyploid chromosome complexes, tripolar and multipolar spindles, binucleate and multinucleate cells. Very few cases of chromosome fragmentation were observed.Accumulation of abnormalities accompanied the passage of ribonuclease across the root as determined by alterations in stainability of the cells with pyronin and fast green. There was no visible modification of stainability of the chromosomes with methyl green or the Feulgen reagent.These results, when compared with those produced by control solutions, indicate that ribonuclease enters the living cell and degrades ribonucleoproteins essential for maintenance of structural and functional integrity. The implications of these results, with respect to the production of aberrations by other agents, are discussed.

BINDING OF LABELED RIBONUCLEIC ACID TO BASIC PROTEINS, A MAJOR DIFFICULTY IN RIBONUCLEIC ACID-DEOXYRIBONUCLEIC ACID HYBRIDIZATION IN FIXED CELLS IN SITU

In an attempt to hybridize H3-ribonucleic acid (RNA) of onion roots to deoxyribonucleic acid of fixed cells in situ it has been found that such RNA binds only to cytoplasmic basic proteins (ribosomal?) as well as nuclear histones or protamines of diverse plant and animal materials. The bound RNA is relatively insensitive to mild RNase digestion. Most of these basic proteins cannot be removed from cells without distorting cell morphology, or without the prior removal of deoxyribonucleic acid. The binding characteristics of H3-RNA and basic proteins parallel alkaline fast green staining of histones. In the formalin-fixed cells, H3-RNA binds to the nucleus only after removal of deoxyribonucleic acid. The binding capacity is abolished after acetylation or deamination of lysine-rich histones; such treatments do not affect the binding ability of arginine-rich histones or protamines.