Effects of polyribonucleotides of known composition on deoxycytidylate and deoxyguanylate kinase activity in Pneumococci.

Polycytidylic acid (poly C) stimulates the activity of deoxycytidylate and deoxyguanylate kinases in cell suspensions of type III pneumococci. Polyadenylic acid (poly A) stimulates the activity of dGMP kinase only. Polyuridylic acid (poly U) or polyinosinic acid (poly I) is inactive in this respect. A selective stimulation of DNA synthesis occurs in comparison to RNA and protein syntheses when the active polymers are added to cell suspensions. Enzyme synthesis, rather than enzyme activity, is affected by the active polyribonucleotides. This is shown by the fact that (a) chloramphenicol inhibits stimulatory effects of the active polymers, (b) omission of amino acids from the suspending medium reduces the stimulatory effects considerably, and (c) the specific activity of dCMP kinase purified from stimulated pneumococci is 4to S-fold higher than dCMP kinase extracted from a similar number of unstimulated pneumococci. The active intracellular materials appear to be oligomers of cytidylic or adenylic acid. Copolymers of various kinds (poly AC, poly UC, or poly GC) are less effective than the homopolymers and a molecular complex of poly C + poly I is completely ineffective. Poly C, but not its oligomers, can form a molecular complex with pneumococcal RNA or denatured pneumococcal DNA in vitro. However, complex formation in vitro is inhibited considerably if the RNA is extracted from cells pre-exposed to oligomers of cytidylic acid or poly C.