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Mol. Cell. Biol., Jun 1995, 3327-3335, Vol 15, No. 6
JL Matthews, MG Zwick and MR Paule
Transcription of large rRNA precursor and 5S RNA were examined during
encystment of Acanthamoeba castellanii. Both transcription units are down
regulated almost coordinately during this process, though 5S RNA
transcription is not as completely shut down as rRNA transcription. The
protein components necessary for transcription of 5S RNA and tRNA were
determined, and fractions containing transcription factors comparable to
TFIIIA, TFIIIB, and TFIIIC, as well as RNA polymerase III and a 3'- end
processing activity, were identified. Regulation of 5S RNA transcription
could be recapitulated in vitro, and the activities of the required
components were compared. In contrast to regulation of precursor rRNA,
there is no apparent change during encystment in the activity of the
polymerase dedicated to 5S RNA expression. Similarly, the transcriptional
and promoter-binding activities of TFIIIC are not altered in parallel with
5S RNA regulation. TFIIIB transcriptional activity is unaltered in
encysting cells. In contrast, both the transcriptional and DNA-binding
activities of TFIIIA are strongly reduced in nuclear extracts from
transcriptionally inactive cells. These results were analyzed in terms of
mechanisms for coordinate regulation of rRNA and 5S RNA expression.
Copyright © 1995, American Society for Microbiology
Coordinate regulation of ribosomal component synthesis in Acanthamoeba castellanii: 5S RNA transcription is down regulated during encystment by alteration of TFIIIA activity
Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins 80523, USA.
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