Two trans-acting rat-brain proteins, MARTA1 and MARTA2, interact specifically with the dendritic targeting element in MAP2 mRNAs

Brain Res Mol Brain Res. 2000 Jun 23;79(1-2):192-201. doi: 10.1016/s0169-328x(00)00114-5.


Different isoforms of the microtubule-associated protein 2 (MAP2) are somatodendritic components of neurons that seem to regulate the stability of the dendritic cytoskeleton. MAP2 localization into dendrites appears to be a complex multicausal mechanism that involves the specific recruitment of MAP2 mRNAs into dendritic compartments. Recently, we have functionally characterized a 640-nucleotide dendritic targeting element (DTE) in the 3' untranslated region (3' UTR) of MAP2 transcripts that mediates extrasomatic mRNA localization in primary neurons (Blichenberg et al. , 1999). In analogy to molecular mechanisms regulating cytoplasmic RNA translocation in other cell systems, we propose that, in vivo, the cis-acting MAP2-DTE interacts with specific protein factors present in neurons. To identify putative trans-acting DTE-binding proteins, we performed in vitro ultraviolet crosslinking assays. Using this experimental system, two 90-kDa and 65-kDa MAP2-RNA trans-acting proteins, MARTA1 and MARTA2, were identified in rat-brain extracts. Both MARTAs bind with high affinity to the MAP2-DTE, but not to other investigated regions of MAP2 transcripts or the somatically restricted alpha-tubulin mRNA. Moreover, MARTA1 and MARTA2 do not bind significantly to other dendritically localized transcripts encoding vasopressin and arg3.1, nor to a dendritic trafficking element from the mRNA encoding the alpha-subunit of the Ca(2+)/calmodulin-dependent protein kinase II. Binding of MARTA1 and MARTA2 to the MAP2-DTE occurs with an affinity in the nanomolar range. Whereas MARTA1 is clearly detectable in crude lysates, cytosolic and ribosomal salt-wash fractions, and in nuclear extracts, MARTA2 is preferentially found in the ribosomal salt-wash preparation. Neither MARTA is restricted to rat brain, and both are present in a number of other rat tissues. Thus, both proteins may be involved in a variety of nuclear and cytoplasmic events that regulate RNA metabolism in different cell types.

MeSH terms

  • 3' Untranslated Regions / genetics
  • 3T3 Cells
  • Animals
  • Brain / metabolism*
  • Dendrites / metabolism*
  • Male
  • Mice
  • Microtubule-Associated Proteins / genetics*
  • Neurons / metabolism*
  • Organ Specificity
  • RNA, Messenger / genetics
  • RNA-Binding Proteins / metabolism*
  • Rats
  • Rats, Wistar
  • Trans-Activators / metabolism*
  • Transcription, Genetic*


  • 3' Untranslated Regions
  • MARTA2 protein, rat
  • Microtubule-Associated Proteins
  • RNA, Messenger
  • RNA-Binding Proteins
  • Trans-Activators