Size and turnover of polyadenylic acid-containing ribonucleic acids in a fragile mutant of Saccharomyces cerevisiae.

Ribonucleic acid-containing polyadenylic acid [poly(A)+-RNA] was studied in lysates from an osmotic-sensitive mutant of Saccharomyces cerevisiae characterized by low nuclease activity. The poly(A)+-RNA fraction, analyzed by electrophoresis in polyacrylamide-formamide gels, constitutes a heterogeneous population of molecules, with molecular weights ranging from 0.2 X 10(6) to 3 X 10(6) and having an average of 1.2 X 10(6). The turnover rate of poly(A)+-RNA was determined by the decay of radioactivity after a cold uracil chase, and the observed half-life of 21 min corresponds to about 10% of the cell doubling time. Poly(A)+-RNA was analyzed by gel electrophoresis under denaturing and non-denaturing conditions. A correlation was established between the apparent secondary structure and the turnover rate of poly(A)+-RNA species.