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The histone mRNA 3' end is required for localization of histone mRNA to polyribosomes
J Sun1, D R Pilch, W F Marzluff
1Institute of Molecular Biophysics, Florida State University, Tallahassee 32306.
Abstract:
The final step in mRNA biosynthesis is transport of the mRNA from the nucleus to the cytoplasm. Histone genes from which the 3' stem-loop has been deleted are transcribed to give RNAs with heterogeneous 3' ends. These RNAs are localized in the nucleus and are stable. Addition of the histone 3' processing signal either on short (< 250 nts) or long (> 1000 nts) transcripts restores 3' processing and transport of the mRNA to the cytoplasm. In addition chimeric histone-U1 snRNA genes which produced RNAs with either histone or U1 3' ends were analyzed. Transcripts which ended with U1 snRNA 3' ends were not efficiently localized to polyribosomes. However, transcripts containing the same sequences including the snRNA 3' end followed by the histone 3' end were present in the cytoplasm on polyribosomes. Taken together these results suggest that the histone 3' end is required for export of histone mRNA to the cytoplasm and association of the mRNA with polyribosomes.
Insights
The histone 3' end signal is crucial for messenger RNA (mRNA) export from the nucleus to the cytoplasm. This signal also ensures proper mRNA localization to polyribosomes for translation.
Area of Science:
- Molecular Biology
- Gene Expression
- RNA Processing
Background:
- Messenger RNA (mRNA) transport from the nucleus to the cytoplasm is a critical step in gene expression.
- Histone mRNA requires specific 3' end processing for efficient export and translation.
Purpose of the Study:
- To investigate the role of the histone 3' end signal in mRNA export and polyribosome association.
- To determine if the histone 3' end is necessary for cytoplasmic transport of histone mRNA.
Main Methods:
- Analysis of histone gene transcripts with deleted 3' stem-loops.
- Addition of histone 3' processing signals to short and long transcripts.
- Construction and analysis of chimeric histone-U1 small nuclear RNA (snRNA) genes.
Main Results:
- Histone RNAs lacking the 3' stem-loop were retained in the nucleus.
- Restoring the histone 3' end signal facilitated 3' processing and cytoplasmic export.
- Transcripts with U1 snRNA 3' ends showed inefficient polyribosome localization, unlike those with the histone 3' end.
Conclusions:
- The histone 3' end is essential for the export of histone mRNA from the nucleus to the cytoplasm.
- This signal is also required for the association of histone mRNA with polyribosomes, enabling translation.