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Structural deviations in a bovine low expression lysozyme-encoding gene active in tissues other than stomach
1Institut für Mikrobiologie und Molekularbiologie, Justus-Liebig-Universität, Giessen, Germany.
Gene
|October 31, 1996
Summary
Bovine lysozyme genes (Lys) show varied expression. Researchers identified a gene variant in granulocytes, revealing promoter mutations and an extra ATG codon explain its weak expression compared to stomach variants.
Area of Science:
- Genomics
- Molecular Biology
- Gene Expression
Background:
- Lysozyme-encoding genes (Lys) form a gene family in ruminants.
- Lys genes exhibit differential expression, with high levels in the stomach (sLys) and low levels in immune cells like granulocytes and macrophages (mLys).
Purpose of the Study:
- To investigate the molecular basis for the differential expression of bovine lysozyme genes, specifically the mLys variant found in granulocytes.
Main Methods:
- Isolation and sequencing of the bovine mLys gene and its promoter region.
- Sequence homology analysis of mLys and sLys variants.
- Primer extension analysis to determine the transcription startpoint (tsp) of the mLys gene.
Main Results:
- The bovine mLys gene, spanning ~9 kb and containing four exons, shows >70% sequence homology with sLys variants, suggesting a common ancestor.
- The transcription startpoint of mLys is located 44 nt upstream compared to bovine sLys and homologous genes in mice and humans.
- Weak mLys expression is attributed to an additional ATG codon in the 5'-UTR and a weakened TATA-box, partially compensated by an upstream mutation creating a substitute promoter.
Conclusions:
- Bovine lysozyme variants originate from a common ancestral gene.
- The distinct promoter sequence and regulatory elements, including an upstream ATG and a mutated TATA-box, account for the low expression of the mLys gene in granulocytes.