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Alternative splicing of the mouse amelogenin primary RNA transcript contributes to amelogenin heterogeneity
E C Lau1, J P Simmer, P Bringas
1University of Southern California, Center for Craniofacial Molecular Biology, Los Angeles 90033.
Abstract:
A heterogeneous population of amelogenin proteins is derived from a single copy of the mouse amelogenin gene. To investigate the one gene--multiple protein enigma, we designed a study to distinguish between alternative splicing and proteolytic cleavage models. A pulse of [35S]methionine labeling demonstrated that multiple amelogenins are synthesized concurrently, a result consistent with an alternative splicing mechanism. Using reverse transcription and polymerase chain reaction we cloned a segment from the 5' end of a mouse amelogenin mRNA and connected it to a previously isolated abbreviated cDNA clone. Four additional cDNAs derived from alternatively spliced amelogenin mRNAs have been cloned and characterized. The five transcripts encode amelogenins 180, 156, 141, 74, and 59 amino acids in length.
Insights
Mouse amelogenin genes produce multiple proteins through alternative splicing, not just protein cutting. This study identified five distinct amelogenin mRNA transcripts, confirming alternative splicing as the mechanism.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- The mouse amelogenin gene produces a heterogeneous population of amelogenin proteins.
- Understanding the mechanism generating protein diversity from a single gene is crucial.
Purpose of the Study:
- To investigate the "one gene--multiple protein" enigma in mouse amelogenins.
- To differentiate between alternative splicing and proteolytic cleavage as the source of protein heterogeneity.
Main Methods:
- Utilized pulse [35S]methionine labeling to assess protein synthesis.
- Employed reverse transcription and polymerase chain reaction (RT-PCR) for mRNA analysis.
- Cloned and characterized cDNA derived from alternatively spliced amelogenin mRNAs.
Main Results:
- Pulse labeling indicated concurrent synthesis of multiple amelogenins, supporting alternative splicing.
- Five distinct alternatively spliced amelogenin mRNA transcripts were identified and cloned.
- These transcripts encode amelogenins of varying lengths: 180, 156, 141, 74, and 59 amino acids.
Conclusions:
- Alternative splicing is the primary mechanism generating the heterogeneity of mouse amelogenin proteins.
- The study provides molecular evidence for multiple amelogenin isoforms derived from a single gene.