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Assembly of alternative multiprotein complexes directs rRNA promoter selectivity
S P Bell1, H M Jantzen, R Tjian
1Howard Hughes Medical Institute, Department of Molecular and Cellular Biology, University of California, Berkeley 94720.
Genes & Development
|June 1, 1990
Summary
Species-specific rRNA transcription relies on distinct interactions between transcription factors SL1 and UBF. While both human and mouse UBF bind DNA similarly, SL1
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Ribosomal RNA (rRNA) transcription is crucial for cell growth and is regulated by specific transcription factors.
- Understanding how transcription factors with similar DNA-binding specificities can drive different transcriptional programs is key to deciphering gene regulation.
- The RNA polymerase I (Pol I) transcription system provides a model to study the mechanisms generating alternative transcription complexes.
Purpose of the Study:
- To investigate the species-specific mechanisms of RNA polymerase I promoter recognition in mice and humans.
- To compare the roles of transcription factors UBF and SL1 in governing species-specific rRNA transcription.
- To elucidate how distinct transcription factor complexes generate functional diversity in rRNA synthesis.
Main Methods:
- Comparative analysis of mouse and human transcription factors involved in rRNA synthesis.
- DNA-binding assays to determine the specificity of UBF and SL1.
- Reconstituted transcription experiments using components from both species.
- Functional assays to assess the distinct activities of mouse and human SL1.
Main Results:
- Human and mouse UBF (Upstream Binding Factor) exhibit identical DNA-binding specificities for rRNA promoters.
- Human SL1 (Selectivity Factor 1) requires UBF for high-affinity DNA binding, while mouse SL1 binds DNA independently.
- Reconstituted transcription experiments showed that mouse and human SL1 possess distinct DNA-binding and transcription activities, despite UBF and Pol I being interchangeable.
- These findings highlight the critical role of multiprotein assembly in Pol I promoter recognition.
Conclusions:
- Species-specific rRNA transcription is mediated by distinct SL1-UBF complex assemblies.
- SL1 plays a crucial role in conferring promoter selectivity, with differential DNA-binding mechanisms between species.
- The study reveals how variations in transcription factor complex formation can lead to functional diversity in rRNA gene transcription.