Heterogeneous nuclear ribonucleoprotein A3, a novel RNA trafficking response element-binding protein.
The cis-acting response element, A2RE, which is sufficient for cytoplasmic mRNA trafficking in oligodendrocytes, binds a small group of rat brain proteins. Predominant among these is heterogeneous nuclear ribonucleoprotein (hnRNP) A2, a trans-acting factor for cytoplasmic trafficking of RNAs bearing A2RE-like sequences. We have now identified the other A2RE-binding proteins as hnRNP A1/A1(B), hnRNP B1, and four isoforms of hnRNP A3. The rat and human hnRNP A3 cDNAs have been sequenced, revealing the existence of alternatively spliced mRNAs. In Western blotting, 38-, 39-, 41-, and 41.5-kDa components were all recognized by antibodies against a peptide in the glycine-rich region of hnRNP A3, but only the 41- and 41.5-kDa bands bound antibodies to a 15-residue N-terminal peptide encoded by an alternatively spliced part of exon 1. The identities of these four proteins were verified by Edman sequencing and mass spectral analysis of tryptic fragments generated from electrophoretically separated bands. Sequence-specific binding of bacterially expressed hnRNP A3 to A2RE has been demonstrated by biosensor and UV cross-linking electrophoretic mobility shift assays. Mutational analysis and confocal microscopy data support the hypothesis that the hnRNP A3 isoforms have a role in cytoplasmic trafficking of RNA.
Ma
Alice S W
AS
Department of Biochemistry and Molecular Biology, The University of Queensland, Brisbane, Queensland 4072, Australia.
Moran-Jones
Kim
K
Shan
Jianguo
J
Munro
Trent P
TP
Snee
Mark J
MJ
Hoek
Keith S
KS
Smith
Ross
R
D000368:Aged; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D001923:Brain Chemistry; D003593:Cytoplasm / Q000378:metabolism; D004252:DNA Mutational Analysis; D005091:Exons; D005260:Female; D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D006801:Humans; D013058:Mass Spectrometry; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010449:Peptide Mapping; D011485:Protein Binding; D012313:RNA / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012261:Ribonucleoproteins / Q000737:chemistry / Q000302:isolation & purification*
D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D012333:RNA, Messenger; D012261:Ribonucleoproteins; C439768:hnRNP A2; D012313:RNA