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

• Published in: Brain research. Molecular brain research. Vol. 79; no. 1; pp. 192 - 201
• Main Authors: Rehbein, Monika, Kindler, Stefan, Horke, Sven, Richter, Dietmar
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 23.06.2000; Elsevier
• Subjects: 3' Untranslated Regions - genetics; 3T3 Cells; Animals; Biochemistry and metabolism; Biological and medical sciences; Brain - metabolism; Central nervous system; Dendrites - metabolism; Dendritic RNA targeting; dendritic targeting element; Extrasomatic localization and translation; Fundamental and applied biological sciences. Psychology; Male; MAP2 protein; MARTA protein; MARTA1 protein; MARTA2 protein; Mice; Microtubule-Associated Proteins - genetics; Neurons - metabolism; Organ Specificity; Rats; Rats, Wistar; RNA, Messenger - genetics; RNA-binding protein; RNA-Binding Proteins - metabolism; Trans-Activators - metabolism; Transcription, Genetic; UV-crosslinking assay; Vertebrates: nervous system and sense organs; Extrasomatic localization and translation; EDTA, ethylenediaminetetraacetic acid; MARTA, MAP2-RNA trans-acting protein; Dendritic RNA targeting; DTE, dendritic targeting element; DTT, dithiothreitol; RNA-binding protein; α-CaMKII, alpha subunit of the Ca 2+/calmodulin-dependent protein kinase II; PMSF, phenylmethylsulfonyl fluoride; MBP, myelin basic protein; PCR, polymerase chain reaction; MAP, microtubule-associated protein; Neural basis of behavior; Vg1, vegetal pole protein 1; RSW, ribosomal salt-wash; UV-crosslinking assay; Vertebrata; Molecular form; Mammalia; Rat; Microtubule associated protein 2; Rodentia; Central nervous system; Cytoskeleton; Gene expression; Protein; Dendrite; Brain (vertebrata)
• ISSN: 0169-328X; 1872-6941
• 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 MA P2- R NA t rans - a cting 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 α-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 α-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.