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A non-canonical start codon in the Drosophila fragile X gene yields two functional isoforms.

Publication ,  Journal Article
Beerman, RW; Jongens, TA
Published in: Neuroscience
May 2011

Fragile X syndrome is caused by the loss of expression of the fragile X mental retardation protein (FMRP). As a RNA binding protein, FMRP functions in translational regulation, localization, and stability of its neuronal target transcripts. The Drosophila homologue, dFMR1, is well conserved in sequence and function with respect to human FMRP. Although dFMR1 is known to express two main isoforms, the mechanism behind production of the second, more slowly migrating isoform has remained elusive. Furthermore, it remains unknown whether the two isoforms may also contribute differentially to dFMR1 function. We have found that this second dFMR1 isoform is generated through an alternative translational start site in the dfmr1 5'UTR. This 5'UTR coding sequence is well conserved in the melanogaster group. Translation of the predominant, smaller form of dFMR1 (dFMR1-S(N)) begins at a canonical start codon (ATG), whereas translation of the minor, larger form (dFMR1-L(N)) begins upstream at a non-canonical start codon (CTG). To assess the contribution of the N-terminal extension toward dFMR1 activity, we generated transgenic flies that exclusively express either dFMR1-S(N) or dFMR1-L(N). Expression analyses throughout development revealed that dFMR1-S(N) is required for normal dFMR1-L(N) expression levels in adult brains. In situ expression analyses showed that either dFMR1-S(N) or dFMR1-L(N) is individually sufficient for proper dFMR1 localization in the nervous system. Functional studies demonstrated that both dFMR1-S(N) and dFMR1-L(N) can function independently to rescue dfmr1 null defects in synaptogenesis and axon guidance. Thus, dfmr1 encodes two functional isoforms with respect to expression and activity throughout neuronal development.

Duke Scholars

Published In

Neuroscience

DOI

EISSN

1873-7544

ISSN

0306-4522

Publication Date

May 2011

Volume

181

Start / End Page

48 / 66

Related Subject Headings

  • Protein Isoforms
  • Neurology & Neurosurgery
  • Gene Expression Regulation
  • Fragile X Mental Retardation Protein
  • Drosophila melanogaster
  • Drosophila Proteins
  • Codon, Initiator
  • Animals
  • 5202 Biological psychology
  • 3209 Neurosciences
 

Citation

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ICMJE
MLA
NLM
Beerman, R. W., & Jongens, T. A. (2011). A non-canonical start codon in the Drosophila fragile X gene yields two functional isoforms. Neuroscience, 181, 48–66. https://doi.org/10.1016/j.neuroscience.2011.02.029
Beerman, R. W., and T. A. Jongens. “A non-canonical start codon in the Drosophila fragile X gene yields two functional isoforms.Neuroscience 181 (May 2011): 48–66. https://doi.org/10.1016/j.neuroscience.2011.02.029.
Beerman, R. W., and T. A. Jongens. “A non-canonical start codon in the Drosophila fragile X gene yields two functional isoforms.Neuroscience, vol. 181, May 2011, pp. 48–66. Epmc, doi:10.1016/j.neuroscience.2011.02.029.
Journal cover image

Published In

Neuroscience

DOI

EISSN

1873-7544

ISSN

0306-4522

Publication Date

May 2011

Volume

181

Start / End Page

48 / 66

Related Subject Headings

  • Protein Isoforms
  • Neurology & Neurosurgery
  • Gene Expression Regulation
  • Fragile X Mental Retardation Protein
  • Drosophila melanogaster
  • Drosophila Proteins
  • Codon, Initiator
  • Animals
  • 5202 Biological psychology
  • 3209 Neurosciences