The heterogeneous nuclear RNA of chicken erythroblasts.

Heterogeneous nuclear RNA (hnRNA) from chicken erythroblasts has a modal molecular weight of 1.6 -10(6) in 99% dimethylsulfoxide. When erythroblasts are labeled continuously with [14C]uridine, nuclear RNA is labeled as a single kinetic component with a half-life of 18 min. After a 10--20 min lag, label appears in cytoplasmic RNA at about 1% of the initial rate of total RNA synthesis. Of the hnRNA sedimenting faster than 28 S ribosomal RNA in both an aqueous sucrose gradient and a subsequent fructose gradient in 99% dimethylsulfoxide, about one-third is polyadenylated, although only about one in 2000 (i.e. about four molecules per cell) contain a globin messenger sequence. The hnRNA of erythroblasts isolated from 5.7- and 11-day chick embryos have the same content of globin messenger sequences as erythroblaasts from anemic adults.