Cinétique de l'incorporation d'uridine (3H) dans des fractions subnucléolaires de cellules d'hépatome ascitique du rat

Summary The kinetics of ( 3 H) uridine labelling of elements resulting from the lysis of the nucleolar apparatus after solubilization of chromatin by heparine is studied ; this enabled us to evidence an early-labelled fraction distinct from the classically described ones in which the maturation of the 45S rRNA precursor takes place. This fraction had not been observed yet. This fraction could correspond either to the material still bound to intra-nucleolar chromatin and removed by heparine, or to the fibrillar elements known to be labelled before granular RNP during the synthesis of rRNAs precursors.