Title: Two Ribosomal DNA‐Binding Factors Interact with a Cluster of Motifs on the 5′ External Transcribed Spacer, Upstream from the Primary Pre‐rRNA Processing Site in a Higher Plant
Abstract: In radish the primary processing site in pre‐rRNA has been mapped to a TTTTCGCGC sequence (motif P) in the 5′ external transcribed spacer (5′ ETS) of the ribosomal DNA (rDNA) [Delcasso‐Tremousaygue, D., Grellet, R, Panabiéres, R, Ananiev, E. & Delseny, M. (1988) Eur. J. Biochem. 172 , 767–776]. The processing site is just downstream of four similar motifs named A 1 , A 2 , A 3 and B. The five motifs constitute cluster A 123 BP. We have described previously that in radish extracts a nuclear protein, nuclear factor B (NF B) specifically binds to motif B [Echeverría, M., Penon, P. & Delseny, M. (1994) Mol. Gen. Genet. 243 , 442–452], Here, by means of electrophoretic‐mobility‐shift assays, we describe an rDNA‐binding activity, nuclear factor D (NF D), that interacts with the A 123 BP cluster. Using various rDNA probes and competitors we show that NF D binds specifically to the A 123 clustered motifs but not to similar B or P motifs. We used sequence‐specific DNA‐affinity chromatography to separate NF D from NF B. DNase I footprinting was used to map the binding site of NF D on the A 123 BP cluster and we compared it with that of NF B on the same probe. The footprint of NF D extends from the A 1 motif to the 5′ end of the NF B‐binding site and includes motifs A 2 and A 3 on each strand. The footprinting of NF B is restricted to motif B and adjacent nucleotides. Thus the NF D‐binding and NF B‐binding sites are distinct but overlap. These two factors bind with a high specificity to the A 123 BP cluster in the radish 5′ ETS. The possibility that these factors regulate rDNA transcription elongation at the level of the primary pre‐rRNA processing site in crucifers is discussed.
Publication Year: 1997
Publication Date: 1997-08-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 18
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