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Revised genomic structure of the human MAGP1 gene and identification of alternate transcripts in human and mouse
F Segade1, T J Broekelmann, R A Pierce
1Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA. fsegade@cellbio.wustl.edu
Abstract:
The human MAGP1 (or MFAP2) and mouse Magp1 genes code for the microfibril-associated glycoprotein-1 (MAGP-1), an extracellular matrix protein of microfibrillar structures. We report a revised 5' genomic structure including the use of a single transcription start site that gives rise to a 32-bp 5' exon spanning a segment of the previously described exon B. No evidence of heterogeneous 5' ends from the use of alternative promoters was found in human tissues and cell lines. We located the genetic marker D1S170 to a position 3 kb downstream of the polyadenylation site. Large-scale comparison of the human and mouse genes revealed conservation of sequence outside the coding exons. Although the 5' flanking regions were found to be divergent certain cis-elements for transcription factors are conserved, including Sp1, AP-2, AP-4, NF-kappaB, and c-ETS motifs. We identified a total of five splice variants in addition to the canonical MAGP1A/Magp1A form. These transcripts are species-specific and are generated by different processing mechanisms. The alternate forms MAGP1A', MAGP1B, and MAGP1C are expressed in human tissues; and the two variants Magp1A" and Magp1D were found only in mouse. The alternatively spliced forms show restricted patterns of expression relative to the canonical isoform.
Insights
The microfibril-associated glycoprotein-1 (MAGP-1) gene structure was revised, revealing a single transcription start site and conserved regulatory elements. Five species-specific splice variants were identified, with distinct expression patterns in human and mouse tissues.
Area of Science:
- Genomics
- Molecular Biology
- Extracellular Matrix Research
Background:
- Microfibril-associated glycoprotein-1 (MAGP-1) is an extracellular matrix protein crucial for microfibrillar structures.
- Understanding the genomic structure and regulation of MAGP1 is essential for comprehending its function.
Purpose of the Study:
- To revise the 5' genomic structure of the human MAGP1 gene.
- To investigate the presence of alternative promoters and transcription start sites.
- To identify and characterize splice variants of MAGP1/Magp1 across species.
Main Methods:
- Genomic DNA analysis to revise the 5' structure.
- Northern blot analysis and RT-PCR to identify splice variants.
- Sequence comparison between human and mouse MAGP1/Magp1 genes.
- Bioinformatic analysis of cis-regulatory elements in flanking regions.
Main Results:
- A revised 5' genomic structure for MAGP1 was determined, utilizing a single transcription start site.
- No evidence of alternative promoters was found in human samples.
- Five species-specific splice variants of MAGP1/Magp1 were identified, with distinct expression profiles.
- Conserved transcription factor binding sites (Sp1, AP-2, AP-4, NF-kappaB, c-ETS) were identified in the divergent 5' flanking regions.
Conclusions:
- The MAGP1 gene exhibits a conserved genomic organization with a single primary transcription start site.
- Alternative splicing generates diverse MAGP-1 isoforms with restricted tissue-specific expression patterns.
- Conserved cis-elements suggest shared regulatory mechanisms despite divergent flanking sequences between human and mouse.