Aldolases a and C are ribonucleolytic components of a neuronal complex that regulates the stability of the light-neurofilament mRNA.
A 68 nucleotide segment of the light neurofilament (NF-L) mRNA, spanning the translation termination signal, participates in regulating the stability of the transcript in vivo. Aldolases A and C, but not B, interact specifically with this segment of the transcript in vitro. Aldolases A and C are glycolytic enzymes expressed in neural cells, and their mRNA binding activity represents a novel function of these isozymes. This unsuspected new activity was first uncovered by Northwestern blotting of a brainstem/spinal cord cDNA library. It was confirmed by two-dimensional fractionation of mouse brain cytosol followed by Northwestern hybridization and protein sequencing. Both neuronal aldolases interact specifically with the NF-L but not the heavy neurofilament mRNA, and their binding to the transcript excludes the poly(A)-binding protein (PABP) from the complex. Constitutive ectopic expression of aldolases A and C accelerates the decay of a neurofilament transgene (NF-L) driven by a tetracycline inducible system. In contrast, mutant transgenes lacking mRNA sequence for aldolase binding are stabilized. Our findings strongly suggest that aldolases A and C are regulatory components of a light neurofilament mRNA complex that modulates the stability of NF-L mRNA. This modulation likely involves endonucleolytic cleavage and a competing interaction with the PABP. Interactions of aldolases A and C in NF-L expression may be linked to regulatory pathways that maintain the highly asymmetrical form and function of large neurons.
Cañete-Soler
Rafaela
R
Division of Neuropathology, Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19103, USA. racansol@mail.med.upenn.edu
Reddy
Konda S
KS
Tolan
Dean R
DR
Zhai
Jinbin
J
D000818:Animals; D015152:Blotting, Northern / Q000379:methods; D015153:Blotting, Western / Q000379:methods; D001921:Brain / Q000378:metabolism; D002460:Cell Line; D002522:Chlorocebus aethiops; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003001:Cloning, Molecular / Q000379:methods; D015180:Electrophoresis, Gel, Two-Dimensional / Q000379:methods; D024202:Electrophoretic Mobility Shift Assay / Q000379:methods; D005634:Fructose-Bisphosphate Aldolase / Q000502:physiology*; D015870:Gene Expression / Q000502:physiology; D005786:Gene Expression Regulation / Q000502:physiology*; D015723:Gene Library; D006801:Humans; D047468:Immunoprecipitation / Q000379:methods; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016900:Neurofilament Proteins / Q000235:genetics / Q000378:metabolism*; D010449:Peptide Mapping / Q000379:methods; D014176:Protein Biosynthesis / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D011993:Recombinant Fusion Proteins; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D014162:Transfection / Q000379:methods
D016900:Neurofilament Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; C044882:neurofilament protein L; D005634:Fructose-Bisphosphate Aldolase