Cellular regulation of ribosomal DNA transcription: Both rat and Xenopus UBF1 stimulate rDNA transcription in 3T3 fibroblasts

Ross Hannan, Toru Arino, Victor Stefanovsky, Lawrence Rothblum*, Tom Moss

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)

Abstract

A novel RNA polymerase I (RPI) driven reporter gene has been used to investigate the in vivo role of the architectural ribosomal transcription factor UBF in gene activation and species specificity. It is shown that the level of UBF overexpression in NIH3T3 cells leads to a proportionate increase in the activities of both reporter and endogenous ribosomal genes. Further, co-expression of UBF antisense RNA suppresses reporter gene expression. Thus, UBF is limiting for ribosomal transcription in vivo and represents a potential endogenous ribosomal gene regulator. In contrast to some in vitro studies, in vivo, the mammalian and Xenopus forms of UBF1 show an equal ability to activate a mouse RPI promoter. This activity is severely impaired in mutants compromised for either dimerization or DNA binding. Similarly, the natural UBF2 splice variant shows a severely impaired capacity to activate RPI transcription. The data strongly suggest that UBF predominantly regulates ribosomal transcription by binding to and activating the ribosomal genes, but does not eliminate a possible secondary role in titrating ribosomal gene repressors such as Rb. Consistent with the DNA folding ability and cellular abundance of the UBF, we suggest that the protein may regulate a structural transition between the potentially active and active chromatin states.

Original languageEnglish
Pages (from-to)1205-1213
Number of pages9
JournalNucleic Acids Research
Volume27
Issue number4
DOIs
Publication statusPublished - Feb 1999
Externally publishedYes

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