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A novel adenovirus-2 E1A mRNA encoding a protein with transcription activation properties
P J Ulfendahl1, S Linder, J P Kreivi
1Department of Medical Genetics, Uppsala University, Sweden.
Abstract:
Two novel adenovirus-2 early region 1A mRNAs, designated 10S and 11S, have been characterized. They differ from the previously described 9S, 12S and 13S mRNAs by having an additional intron removed during mRNA maturation. The 10S and 11S mRNAs encode proteins with mol. wts of 30 and 35 kd. These proteins are encoded in the same translational reading frame as the 12S and 13S mRNA products and differ by lacking 72 amino acids between position 27 and 98. A functional analysis showed that both the 10S and 11S mRNA products are non-essential for lytic virus growth, and, furthermore, defective in cellular transformation. Interestingly the 11S mRNA product functioned as an efficient transcriptional activator in transient expression assays but was very ineffective as a gene activator during virus growth. Moreover, the virus expressing the 11S cDNA failed to block host cell gene expression although substantial amounts of late proteins were expressed. From the biological properties of the E1A cDNA mutants it was possible to localize two functional domains in the E1A proteins; one region required for transcriptional activation (amino acids 140-185), and a second domain required for adenovirus transformation and the control of viral and cellular gene expression during a lytic infection (amino acids 27-98).
Insights
Two new adenovirus E1A mRNAs, 10S and 11S, were identified. These variants are non-essential for viral growth and cellular transformation, with distinct functional domains identified within E1A proteins.
Area of Science:
- Molecular Biology
- Virology
- Gene Expression
Background:
- Adenovirus early region 1A (E1A) proteins regulate viral and cellular gene expression.
- Previously identified E1A mRNAs include 9S, 12S, and 13S variants.
Purpose of the Study:
- To characterize two novel adenovirus E1A mRNAs, 10S and 11S.
- To investigate the functional roles of the proteins encoded by these new E1A mRNAs.
- To map functional domains within E1A proteins.
Main Methods:
- mRNA characterization and sequencing.
- Protein molecular weight determination.
- Functional analysis through lytic virus growth, cellular transformation assays, and transient expression assays.
- Analysis of E1A cDNA mutants.
Main Results:
- The 10S and 11S mRNAs encode 30 kDa and 35 kDa proteins, respectively, differing from 12S/13S products by a 72 amino acid deletion.
- These novel E1A proteins are non-essential for lytic adenovirus growth and are defective in cellular transformation.
- The 11S protein is a potent transcriptional activator in transient assays but ineffective during lytic infection.
- A functional domain for transcriptional activation (aa 140-185) and a domain for transformation and gene expression control (aa 27-98) were localized.
Conclusions:
- Adenovirus E1A gene expression generates multiple mRNA variants with distinct protein products.
- The 10S and 11S E1A proteins play non-essential roles in lytic viral replication and transformation.
- Specific functional domains within E1A proteins are critical for transcriptional activation, cellular transformation, and regulation of gene expression during infection.