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Origin of the two mRNA species for the human neurofilament light gene
L Beaudet1, G Charron, J P Julien
1Centre for Research in Neuroscience, McGill University, Montréal, Que., Canada.
Abstract:
The human neurofilament light (hNF-L) gene yields two major species of mRNAs of 2.4 and 3.8 kilobases (kb) in size. To investigate the origin of these two mRNAs, we have analyzed in transgenic mice the expression of hNF-L DNA fragments including different lengths of 5'-flanking regions. The finding that the 3.8-kb mRNA species is produced by a hNF-L transgene that includes only the proximal promoter region (-0.3 kb) demonstrates that both the 2.4- and 3.8-kb mRNAs are derived from the same site of transcription initiation. Sequencing of the 3' untranslated region of the hNF-L gene revealed the presence of multiple AATAAA polyadenylation signals. We conclude from Northern blotting experiments using probes spanning various regions of the hNF-L gene that the 2.4- and 3.8-kb mRNAs originate from the selective use of polyadenylation signals located 1.4 kb apart.
Insights
The human neurofilament light (hNF-L) gene produces two mRNA types. Selective use of polyadenylation signals explains the origin of these distinct hNF-L mRNA lengths.
Area of Science:
- Molecular Biology
- Neuroscience
Background:
- The human neurofilament light (hNF-L) gene is known to produce two major mRNA species.
- These mRNA variants differ in size, measuring 2.4 and 3.8 kilobases (kb).
Purpose of the Study:
- To investigate the molecular mechanisms underlying the generation of the two hNF-L mRNA variants.
- To determine if the different mRNA sizes originate from distinct transcription start sites or alternative polyadenylation.
Main Methods:
- Analysis of hNF-L gene expression in transgenic mice.
- Utilizing DNA fragments with varying 5'-flanking regions.
- Sequencing of the 3' untranslated region (UTR) of the hNF-L gene.
- Northern blotting with probes specific to different gene regions.
Main Results:
- Transgenic expression confirmed that both 2.4-kb and 3.8-kb mRNAs initiate from the same transcription start site.
- Sequencing revealed multiple AATAAA polyadenylation signals within the hNF-L 3' UTR.
- Northern blot analysis indicated that the mRNA variants arise from differential usage of two polyadenylation signals separated by 1.4 kb.
Conclusions:
- The two hNF-L mRNA species (2.4-kb and 3.8-kb) are generated from a single transcription start site.
- Alternative polyadenylation, utilizing distinct polyadenylation signals, is responsible for the size heterogeneity of hNF-L mRNAs.