Figure 6
Model of changes to the pol III transcription machinery that accompany differentiation of F9 EC cells into PE. In EC cells, tRNA genes are transcribed very actively, reflecting the availability of TFIIIB, c-Myc and activated Erk. Differentiation is accompanied by decreased levels of TFIIIB and c-Myc, as well as inactivation of Erk and induction of RB. PE cells contain relatively little TFIIIB, which is deprived of activators and liable to inhibition by RB; as a consequence, transcription of tRNA genes is severely restricted.