Similar regulation of human inducible nitric-oxide synthase expression by different isoforms of the RNA-binding protein AUF1.
The ARE/poly-(U) binding factor 1 (AUF1), a protein family consisting of four isoforms, is believed to mediate mRNA degradation by binding to AU-rich elements (ARE). However, evidence exists that individual AUF1 isoforms may stabilize ARE-containing mRNAs. The 3'-untranslated region of the human inducible nitric-oxide synthase (iNOS) contains five AREs, which promote RNA degradation. We have recently shown that the RNA-binding protein KSRP is critically involved in the decay of the iNOS mRNA. In this study we examined the effects of the individual AUF1 isoforms on iNOS expression. Overexpression of each AUF1 isoform reduces iNOS expression on mRNA and protein levels to the same extent by modulation of mRNA stability. Accordingly, knockdown of all or individual AUF1 isoforms by an RNA interference approach enhances iNOS expression. The AUF1 effect on iNOS expression is dependent on the iNOS 3'-untranslated region sequence, as demonstrated in transfection experiments with a reporter mRNA. Binding studies showed that all AUF1 isoforms interact with the same AU-rich region in the iNOS-3'-untranslated region. Cytokine stimulation altered intracellular AUF1 binding activities. These data demonstrate that AUF1 is an important factor that promotes iNOS mRNA degradation. Furthermore, all individual AUF1 isoforms act in a similar manner.
Pautz
Andrea
A
Department of Pharmacology, Johannes Gutenberg University, Obere Zahlbacher Strasse 67, D-55101 Mainz, Germany.
Linker
Katrin
K
Department of Pharmacology, Johannes Gutenberg University, Obere Zahlbacher Strasse 67, D-55101 Mainz, Germany.
Altenhöfer
Sebastian
S
Department of Pharmacology, Johannes Gutenberg University, Obere Zahlbacher Strasse 67, D-55101 Mainz, Germany.
Heil
Sebastian
S
Department of Pharmacology, Johannes Gutenberg University, Obere Zahlbacher Strasse 67, D-55101 Mainz, Germany.
Schmidt
Nadine
N
Department of Pharmacology, Johannes Gutenberg University, Obere Zahlbacher Strasse 67, D-55101 Mainz, Germany.
Art
Julia
J
Department of Pharmacology, Johannes Gutenberg University, Obere Zahlbacher Strasse 67, D-55101 Mainz, Germany.
Knauer
Shirley
S
Molecular and Cellular Oncology, University Hospital of Mainz, Langenbeckstrasse 1, D-55101 Mainz, Germany.
Stauber
Roland
R
Molecular and Cellular Oncology, University Hospital of Mainz, Langenbeckstrasse 1, D-55101 Mainz, Germany.
Sadri
Navid
N
Department of Microbiology, New York University School of Medicine, New York, New York 10003.
Pont
Adam
A
Department of Microbiology, New York University School of Medicine, New York, New York 10003.
Schneider
Robert J
RJ
Department of Microbiology, New York University School of Medicine, New York, New York 10003.
Kleinert
Hartmut
H
Department of Pharmacology, Johannes Gutenberg University, Obere Zahlbacher Strasse 67, D-55101 Mainz, Germany. Electronic address: kleinert@mail.uni-mainz.de.
D020413:3' Untranslated Regions; D001483:Base Sequence; D045744:Cell Line, Tumor; D017931:DNA Primers; D000081035:Heterogeneous Nuclear Ribonucleoprotein D0; D034502:Heterogeneous-Nuclear Ribonucleoprotein D / Q000502:physiology*; D006801:Humans; D047468:Immunoprecipitation; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000502:physiology*; D034622:RNA Interference
D020413:3' Untranslated Regions; D017931:DNA Primers; C000630986:HNRNPD protein, human; D000081035:Heterogeneous Nuclear Ribonucleoprotein D0; D034502:Heterogeneous-Nuclear Ribonucleoprotein D; D020033:Protein Isoforms; D052247:Nitric Oxide Synthase Type II