Synthesis of histone messenger RNAs by RNA polymerase II in nuclei from S phase HeLa S₃ cells

Abstract

Nuclei were isolated from synchronized HeLa S₃ cells and transcribed utilizing their endogenous RNA polymerases. Our data suggest that S phase nuclei are capable of synthesizing histone mRNA sequences while nuclei from G₁ phase cells are not. Transcription of histone mRNA sequences by S phase nuclei can be abolished completely by low levels of α-amanitin (1.0 μg/ml, a concentration which completely inhibits RNA polymerase II). From these results it appears that transcription of the histone mRNA sequences occurs during the S phase but not during the G₁ phase of the cell cycle and that RNA polymerase II is responsible for histone gene readout.