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Tiny T antigen: an autonomous polyomavirus T antigen amino-terminal domain
1Department of Biochemistry, University of Missouri-Columbia, 65121, USA. bcmriley@muccmail.missouri.edu
Abstract:
Three mRNAs from the murine polyomavirus early region encode the three well-characterized tumor antigens. We report the existence of a fourth alternatively spliced mRNA which encodes a fourth tumor antigen, tiny T antigen, which comprises the amino-terminal domain common to all of the T antigens but is extended by six unique amino acid residues. The amount of tiny T antigen in infected cells is small because of its short half-life. Tiny T antigen stimulates the ATPase activity of Hsc70, most likely because of its DnaJ-like motif. The common amino-terminal domain may interface with chaperone complexes to assist the T antigens in carrying out their diverse functions of replication, transcription, and transformation in the appropriate cellular compartments.
Insights
Researchers discovered a fourth tumor antigen, tiny T antigen, encoded by an alternatively spliced mRNA in murine polyomavirus. This tiny T antigen interacts with chaperone complexes, potentially aiding viral replication and transformation.
Area of Science:
- Virology
- Molecular Biology
- Oncology
Background:
- Murine polyomavirus (MPyV) early region encodes three well-characterized tumor antigens.
- These tumor antigens are crucial for viral replication, transcription, and cellular transformation.
Purpose of the Study:
- To identify and characterize novel alternatively spliced mRNAs and their encoded proteins from the MPyV early region.
- To investigate the functional properties and cellular interactions of any newly discovered tumor antigens.
Main Methods:
- Analysis of MPyV early region transcripts to identify alternative splicing events.
- Molecular cloning and expression of the novel mRNA to produce the putative tiny T antigen.
- Biochemical assays to assess the ATPase activity of Hsc70 in the presence of tiny T antigen.
- Bioinformatic analysis to identify functional motifs within the tiny T antigen sequence.
Main Results:
- Identification of a fourth, alternatively spliced mRNA encoding a tiny T antigen.
- Tiny T antigen shares a common N-terminal domain with other T antigens but possesses a unique C-terminal extension.
- Tiny T antigen exhibits a short half-life in infected cells.
- Tiny T antigen stimulates the ATPase activity of Hsc70, suggesting a DnaJ-like function.
Conclusions:
- A novel tiny T antigen, encoded by an alternatively spliced mRNA, exists in murine polyomavirus-infected cells.
- The DnaJ-like motif in tiny T antigen likely mediates its interaction with Hsc70 chaperone complexes.
- The common N-terminal domain of T antigens may facilitate their interaction with chaperone machinery, supporting viral functions.