A novel RNA polymerase I-dependent RNase activity that shortens nascent transcripts from the 3′ end

A novel RNA polymerase I-dependent RNase activity that shortens nascent transcripts from the 3′ end

Herbert Tschochner*

Institut für Biochemie I, Universität Heidelberg, Im Neuenheimer Feld 328, D-69120 Heidelberg, Germany

Abstract

A novel RNase activity was identified in a yeast RNA polymerase I (pol I) in vitro transcription system. Transcript cleavage occurred at the 3′ end and was dependent on the presence of ternary pol I/DNA/RNA complexes and an additional protein factor not identical to transcription factor IIS (TFIIS). Transcript cleavage was observed both on arrested complexes at the linearized ends of the transcribed DNA and on intrinsic blocks of the DNA template. Shortened transcripts that remained associated within the ternary complexes were capable of resuming RNA chain elongation. Possible functions of the nuclease for transcript elongation or termination are discussed.

Footnotes

↵ * e-mail: IM4{at}ix.urz.uni-heidelberg.de.
Roger Kornberg, Stanford University School of Medicine, Stanford, CA
Abbreviations: pol I, II, and III, RNA polymerase I, II, and III, respectively; PMSF, phenylmethylsulfonylfluoride.