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A conserved sequence in the argininosuccinate synthetase 3′ untranslated region binds specifically to carbamyl phosphate synthetase (ammonia), the first enzyme in the pathway of urea synthesis
Author(s) -
Cohen Natalie S.,
Zhang Zesong,
Tran Kathy,
Salles Arghavan
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.786.3
Subject(s) - argininosuccinate synthase , carbamyl phosphate , carbamoyl phosphate synthetase , biochemistry , biology , microbiology and biotechnology , argininosuccinate lyase , untranslated region , enzyme , cytoplasm , rna , messenger rna , gene , urea cycle , amino acid , arginine , citrulline
The five enzymes of urea synthesis in mammalian liver are in separate cellular compartments: the first two are in the mitochondrial matrix and the next three in the cytoplasm. The protein levels of all of the enzymes are coordinately regulated at both the transcriptional and post‐transcriptional levels. The pathway is highly ordered in situ, with the three cytoplasmic enzymes organized around the mitochondria. The mRNAs of two of the cytoplasmic enzymes, argininosuccinate synthetase (ASS) and argininosuccinate lyase, are also localized around the mitochondria. The ASS 3′ untranslated region (UTR) has a conserved sequence containing motifs implicated in post‐transcriptional regulation of various mRNAs in several organisms; we therefore did RNA/protein binding studies with this UTR and rat hepatocyte cytoplasmic extracts. Deletions and mutations showed that the conserved sequence was essential for protein binding. A 144 kDa protein that bound specifically to the ASS 3′UTR was obtained by RNA affinity chromatography, and identified by tandem mass spectrometry as an N‐terminally‐cleaved form of carbamyl phosphate synthetase (ammonia) (CPS I), the first enzyme of the pathway. Tissue transglutaminase bound the UTR non‐specifically. The results strongly suggest that there may be some CPS I in the cytoplasm that is involved in the post‐transcriptional regulation of ASS mRNA. Support: NSF #MCB 9601421 & 9983005.