Functional significance for a heterogenous ribonucleoprotein A18 signature RNA motif in the 3'-untranslated region of ataxia telangiectasia mutated and Rad3-related (ATR) transcript.
The predominantly nuclear heterogenous ribonucleoprotein A18 (hnRNP A18) translocates to the cytosol in response to cellular stress and increases translation by specifically binding to the 3'-untranslated region (UTR) of several mRNA transcripts and the eukaryotic initiation factor 4G. Here, we identified a 51-nucleotide motif that is present 11.49 times more often in the 3'-UTR of hnRNP A18 mRNA targets than in the UniGene data base. This motif was identified by computational analysis of primary sequences and secondary structures of hnRNP A18 mRNA targets against the unaligned sequences. Band shift analyses indicate that the motif is sufficient to confer binding to hnRNP A18. A search of the entire UniGene data base indicates that the hnRNP A18 motif is also present in the 3'-UTR of the ataxia telangiectasia mutated and Rad3-related (ATR) mRNA. Validation of the predicted hnRNP A18 motif is provided by amplification of endogenous ATR transcript on polysomal fractions immunoprecipitated with hnRNP A18. Moreover, overexpression of hnRNP A18 results in increased ATR protein levels and increased phosphorylation of Chk1, a preferred ATR substrate, in response to UV radiation. In addition, our data indicate that inhibition of casein kinase II or GSK3beta significantly reduced hnRNP A18 cytosolic translocation in response to UV radiation. To our knowledge, this constitutes the first demonstration of a post-transcriptional regulatory mechanism for ATR activity. hnRNP A18 could thus become a new target to trigger ATR activity as back-up stress response mechanisms to functionally compensate for absent or defective responders.
Yang
Ruiqing
R
Department of Radiation Oncology, the Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
Zhan
Ming
M
Nalabothula
Narasimha Rao
NR
Yang
Qingyuan
Q
Indig
Fred E
FE
Carrier
France
F
D020413:3' Untranslated Regions; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D064007:Ataxia Telangiectasia Mutated Proteins; D047390:Casein Kinase II / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics*; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000235:genetics*; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D034441:Heterogeneous-Nuclear Ribonucleoproteins / Q000235:genetics*; D006801:Humans; D018613:Microscopy, Confocal / Q000379:methods; D008969:Molecular Sequence Data; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D012313:RNA / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D025521:Tumor Suppressor Proteins / Q000235:genetics*
D020413:3' Untranslated Regions; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D025521:Tumor Suppressor Proteins; D012313:RNA; C576324:ATM protein, human; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D047390:Casein Kinase II; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D017346:Protein Serine-Threonine Kinases; D038362:Glycogen Synthase Kinase 3