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Epstein-Barr virus bicistronic mRNAs generated by facultative splicing code for two transcriptional trans-activators
E Manet1, H Gruffat, M C Trescol-Biemont
1Laboratoire de Virologie Moléculaire, Ecole Normale Supérieure de Lyon, CNRS (UMR13), France.
The EMBO Journal
|June 1, 1989
Summary
Epstein-Barr virus (EBV) EB1 transactivator can be produced from three mRNAs. Two bicistronic mRNAs also express the R transactivator, impacting EBV productive cycle.
Area of Science:
- Molecular Virology
- Gene Regulation
- Epigenetics
Background:
- The Epstein-Barr virus (EBV) genome encodes multiple transcriptional transactivators crucial for its life cycle.
- The EB1 protein, encoded by the BZLF1 ORF, is a key regulator that can induce the EBV productive cycle in infected B cells.
Purpose of the Study:
- To investigate the molecular mechanisms underlying EB1 expression and its regulation.
- To characterize the different messenger RNAs (mRNAs) encoding EB1 and identify potential co-expressed proteins.
Main Methods:
- Cloning and characterization of full-length complementary DNAs (cDNAs) encoding EB1.
- Analysis of mRNA transcripts originating from two distinct promoters (P1 and P2).
- Identification and functional analysis of expressed proteins using specific antisera and reporter assays.
Main Results:
- EB1 expression is driven by at least two promoters (P1 and P2), generating three overlapping mRNAs.
- A 1 kb mRNA from P1 encodes EB1 exclusively.
- Two larger mRNAs (3 and 4 kb) are bicistronic, encoding both EB1 and the R transactivator, and are produced via facultative splicing.
- Both EB1 and R proteins were confirmed to be expressed from the bicistronic mRNAs.
- The expressed EB1 and R proteins were shown to activate transcription from the EBV early promoter DR.
Conclusions:
- EB1 expression is regulated by alternative promoters and splicing, leading to the production of distinct mRNA isoforms.
- The discovery of bicistronic mRNAs encoding both EB1 and R provides new insights into the coordinated regulation of EBV gene expression.
- These findings elucidate a complex regulatory mechanism controlling the EBV productive cycle, involving multiple transactivators produced from a single transcriptional unit.