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Genomic organization of the mouse granzyme A gene. Two mRNAs encode the same mature granzyme A with different leader
R J Hershberger1, H K Gershenfeld, I L Weissman
1Department of Pathology, Stanford Medical Center, California 94305.
Abstract:
Granzyme A is a serine protease that, together with the other granular components of cytotoxic T lymphocyte (CTL) cells, has been implicated in the cytolysis process. We report here two different messages and the genomic organization of the mouse granzyme A gene. The granzyme A gene is composed of six exons spanning 7 kilobases. Alternative splicing of the second exon results in the two transcripts. The two mRNA species encode the same mature granzyme A protein but with different leader sequences. The first (HF1) encodes a typical leader signal sequence similar to other granzymes, but the second (HF2) putative leader sequence is different and less hydrophobic. Both messages are present in cultured CTL cell lines and in normal lymphoid tissues. They are both induced when CTL cells are activated in vitro or in vivo. Both messages can be translated in vitro, although the HF1 message appears to be much more efficient as a template. The putative 5' promoter region of the HF gene sequenced (500 base pairs of upstream sequences) contains no well defined promoter sequences aside from the TATA box. The results suggest that (a) granzyme A may be produced with putative different leader sequences from two different mRNAs; (b) this may provide a model system for studying alternate splicing and the evolution of a complex enzymatic system in an organelle; and (c) the genomic DNA reported will be useful for studying transcription regulations involved in controlling the specific expression pattern of this gene.
Insights
Mouse granzyme A, a key cytotoxic T lymphocyte (CTL) protease, is produced from two distinct mRNA transcripts due to alternative splicing. These transcripts encode the same mature protein but differ in their leader sequences, impacting protein targeting.
Area of Science:
- Immunology
- Molecular Biology
- Genetics
Background:
- Granzyme A is a serine protease crucial for cytotoxic T lymphocyte (CTL)-mediated cytolysis.
- Understanding the regulation of Granzyme A expression is vital for comprehending immune responses.
Purpose of the Study:
- To investigate the genomic organization and alternative splicing of the mouse Granzyme A gene.
- To characterize the two distinct mRNA transcripts and their encoded proteins.
Main Methods:
- Analysis of mouse Granzyme A gene structure, including exon-intron organization.
- Identification and characterization of two mRNA species via alternative splicing.
- In vitro translation studies to assess mRNA efficiency.
- Sequencing of the 5' promoter region.
Main Results:
- The mouse Granzyme A gene comprises six exons over 7 kilobases.
- Alternative splicing of the second exon generates two mRNA transcripts (HF1 and HF2).
- Both transcripts encode the same mature Granzyme A but with different leader sequences (HF1 typical, HF2 atypical).
- Both mRNA species are found in CTLs and lymphoid tissues, induced upon CTL activation.
- HF1 mRNA is a more efficient template for in vitro translation.
Conclusions:
- Granzyme A can be produced with distinct leader sequences from two alternatively spliced mRNAs.
- This system offers a model for studying alternative splicing and enzyme evolution within organelles.
- The characterized genomic DNA is valuable for research into Granzyme A gene transcription regulation.