Regulation of Tyrosine Hydroxylase mRNA Stability by Protein-binding, Pyrimidine-rich Sequence in the 3′-Untranslated Region

• Published in: The Journal of biological chemistry 1999-01, Vol.274 (4), p.2532
• Main Authors: Waltke R. Paulding, Maria F. Czyzyk-Krzeska
• Format: Article
• Language: English
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.274.4.2532

The stability of mRNA for tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine synthesis, is regulated by oxygen tension in the pheochromocytoma-derived PC12 cell line. We previously identified a pyrimidine-rich 27-base-long protein-binding sequence in the 3′-untranslated region of TH mRNA that is associated with hypoxia-inducible formation of a ribonucleoprotein complex (hypoxia-inducible protein-binding site (HIPBS)). In this study, we show that HIPBS is an mRNA stabilizing element necessary for both constitutive and hypoxia-regulated stability of TH mRNA. The mutations within this sequence that abolish protein binding markedly decrease constitutive TH mRNA stability and ablate its hypoxic regulation. A short fragment of TH mRNA that contains the wild-type HIPBS confers the increased mRNA stability to the reporter chloramphenicol acetyltransferase mRNA. However, it is not sufficient to confer hypoxic regulation. The HIPBS element binds two isoforms of a 40-kDa poly(C)-binding protein (PCBP). Hypoxia induces expression of the isoform 1, PCBP 1 , but not the isoform 2, PCBP 2 , in PC12 cells.