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Dissecting Innate Immune Signaling in Viral Evasion of Cytokine Production
Published on: March 2, 2014
Characterization and regulation of essential murine cytomegalovirus genes m142 and m143
Laura K Hanson1, Bridget L Dalton, Laura F Cageao
1Department of Microbiology and Molecular Cell Biology, Eastern Virginia Medical School, Norfolk, VA 23501, USA. hansonlk@evms.edu
Abstract:
US22 gene family members m142 and m143 are essential for replication of murine cytomegalovirus (MCMV). Their transcripts are produced with immediate-early kinetics, but little else is known about these viral genes. Unlike their transcripts, the m142 and m143 gene products (pm142, pm143) were not expressed until early times post-infection, with levels increasing over the course of infection. Both pm142 and pm143 were predominantly cytoplasmic, but cellular fractionation studies confirmed that the proteins were present in the nucleus as well. In addition, pm142 was detected within the virion. Both the m142 and m143 promoters were strongly upregulated by viral infection or by MCMV IE1. However, UV-inactivated virus and IE3 upregulated only the m142 promoter. When tested for transcriptional transactivating activity, neither m142 nor m143 demonstrated significant activity, either alone or in combination with the major immediate-early gene products. This failure to transactivate, along with their essential nature, makes m142 and m143 unique among the immediate-early genes of the US22 gene family.
Insights
Murine cytomegalovirus (MCMV) US22 gene family members m142 and m143 are crucial for viral replication. These essential proteins, pm142 and pm143, are expressed later than their transcripts and lack transactivating function, distinguishing them from other MCMV immediate-early genes.
Area of Science:
- Virology
- Molecular Biology
- Gene Regulation
Background:
- Murine cytomegalovirus (MCMV) immediate-early (IE) genes play critical roles in viral replication and pathogenesis.
- The US22 gene family within MCMV encodes proteins with diverse functions, but the specific roles of m142 and m143 remain largely uncharacterized.
- Understanding the expression kinetics and functional properties of these IE genes is essential for deciphering MCMV infection cycles.
Purpose of the Study:
- To investigate the expression patterns and functional characteristics of the MCMV m142 and m143 genes and their protein products.
- To determine the transcriptional regulation of m142 and m143 promoters by viral factors.
- To assess the transactivating potential of m142 and m143 proteins.
Main Methods:
- Analysis of m142 and m143 transcript and protein expression kinetics post-MCMV infection.
- Cellular fractionation to determine the subcellular localization of pm142 and pm143.
- Promoter activity assays to evaluate the regulatory effects of viral infection and IE proteins on m142 and m143 promoters.
- Transactivation assays to test the ability of m142 and m143 to regulate gene expression.
Main Results:
- m142 and m143 transcripts are immediate-early, while proteins (pm142, pm143) are expressed with early kinetics and increase during infection.
- Both pm142 and pm143 are found in the cytoplasm and nucleus; pm142 is also detected in the virion.
- MCMV infection and IE1 strongly upregulate both m142 and m143 promoters, while UV-inactivated virus and IE3 primarily upregulate the m142 promoter.
- Neither m142 nor m143 exhibited significant transcriptional transactivating activity.
Conclusions:
- The m142 and m143 genes are essential for MCMV replication.
- The distinct expression timing and lack of transactivation differentiate pm142 and pm143 from other characterized MCMV IE proteins.
- These findings highlight the unique nature of m142 and m143 within the US22 gene family and their specialized roles in the MCMV life cycle.
