Tracking COL1A1 RNA in osteogenesis imperfecta: Splice-defective transcripts initiate transport from the gene but are retained within the SC35 domain

Citation
C. Johnson et al., Tracking COL1A1 RNA in osteogenesis imperfecta: Splice-defective transcripts initiate transport from the gene but are retained within the SC35 domain, J CELL BIOL, 150(3), 2000, pp. 417-431
Citations number
78
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Cell & Developmental Biology
Journal title
JOURNAL OF CELL BIOLOGY
ISSN journal
0021-9525 → ACNP
Volume
150
Issue
3
Year of publication
2000
Pages
417 - 431
Database
ISI
SICI code
0021-9525(20000807)150:3<417:TCRIOI>2.0.ZU;2-0
Abstract
This study illuminates the intra-nuclear fate of COL1A1 RNA in osteogenesis imperfecta (OI) Type I. Patient fibroblasts were shown to carry a heterozy gous defect in splicing of intron 26, blocking mRNA export. Both the normal and mutant allele associated with a nuclear RNA track, a localized accumul ation of posttranscriptional RNA emanating to one side of the gene. Both tr acks had slightly elongated or globular morphology, but mutant tracks were cytologically distinct in that they lacked the normal polar distribution of intron 26. Normal COL1A1 RNA tracks distribute throughout an SC-35 domain, from the gene at the periphery. Normally, almost all 50 COL1A1 introns are spliced at or adjacent to the gene, before mRNA transits thru the domain. Normal COL1A1 transcripts may undergo maturation needed for export within t he domain such as removal of a slow-splicing intron (shown for intron 24), after which they may disperse. Splice-defective transcripts still distribut e thru the SC-35 domain, moving similar to 1-3 mu m from the gene. However, microfluorimetric analyses demonstrate mutant transcripts accumulate to ab normal levels within the track and domain. Hence, mutant transcripts initia te transport from the gene, but are impeded in exit from the SC-35 domain,T his identifies a previously undefined step in mRNA export, involving moveme nt through an SC-35 domain. A model is presented in which maturation and re lease for export of COL1A1 mRNA is linked to rapid cycling of metabolic com plexes within the splicing factor domain, adjacent to the gene. This paradi gm may apply to SC-35 domains more generally, which we suggest may be nucle ated at sites of high demand and comprise factors being actively used to fa cilitate expression of associated loci.