Apobec-1 protects intestine from radiation injury through posttranscriptional regulation of cyclooxygenase-2 expression.

Abstract

BACKGROUND & AIMS:

This study aimed to determine the role of the RNA binding protein apobec-1 in radioprotection of the intestine.

METHODS:

Apobec-1-deleted mice (APOBEC-1(-/-)) and wild-type controls were treated with 12 Gy of whole-body gamma-irradiation in a cesium irradiator. The number of surviving intestinal crypts was assessed 3.5 days after irradiation by using a clonogenic assay. Cyclooxygenase-2 messenger RNA and protein expression were determined by real-time polymerase chain reaction and Western blot, respectively. RNA stability was studied by examining the turnover of a chimeric transcript containing the cyclooxygenase-2 3' untranslated region cloned downstream of luciferase complementary DNA. Apobec-1 binding to the cyclooxygenase-2 3' untranslated region was studied by electrophoretic mobility shift and UV crosslinking assays.

RESULTS:

After gamma-irradiation, the survival of intestinal stem cells decreased significantly in APOBEC-1(-/-) mice. In wild-type mice treated with lipopolysaccharide before gamma-irradiation, intestinal stem cells were protected by marked increases in prostaglandin E 2 mediated by cyclooxygenase-2. No such effect was observed in the APOBEC-1(-/-) mice. The mechanism of this radioprotective effect involves the binding of apobec-1 to AU-rich sequences in the first 60 nucleotides of the 3' untranslated region of cyclooxygenase-2. Upon binding to the AU-rich sequences, apobec-1 stabilizes cyclooxygenase-2 messenger RNA. This stabilization process does not seem to be mediated by p38 mitogen-activated protein kinase pathways.

CONCLUSIONS:

Lipopolysaccharide increases intestinal stem cell survival through apobec-1-mediated regulation of cyclooxygenase-2 messenger RNA stability.

• Authors: Shrikant Anant, Nabendu Murmu, Courtney W Houchen, Debnath Mukhopadhyay, Terrence E Riehl, Stephen G Young, Aubrey R Morrison, William F Stenson, Nicholas O Davidson
• Journal: Gastroenterology (Gastroenterology) Vol. 127 Issue 4 Pg. 1139-49 (Oct 2004) ISSN: 0016-5085 [Print] United States
• PMID: 15480992 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• 3' Untranslated Regions
• Imidazoles
• Isoenzymes
• Lipopolysaccharides
• Pyridines
• RNA, Messenger
• Cyclooxygenase 2
• Prostaglandin-Endoperoxide Synthases
• Mitogen-Activated Protein Kinases
• p38 Mitogen-Activated Protein Kinases
• APOBEC-1 Deaminase
• Apobec1 protein, mouse
• Cytidine Deaminase
• 4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole

Topics

• 3' Untranslated Regions
• APOBEC-1 Deaminase
• Animals
• Cyclooxygenase 2
• Cytidine Deaminase (physiology)
• Gamma Rays
• Gene Expression Regulation, Enzymologic
• Imidazoles (pharmacology)
• Intestinal Mucosa (metabolism)
• Intestines (radiation effects)
• Isoenzymes (genetics)
• Lipopolysaccharides (pharmacology)
• Mice
• Mice, Inbred C57BL
• Mitogen-Activated Protein Kinases (physiology)
• Prostaglandin-Endoperoxide Synthases (genetics)
• Pyridines (pharmacology)
• RNA, Messenger (analysis)
• Radiation Injuries (prevention & control)
• Stem Cells (radiation effects)
• p38 Mitogen-Activated Protein Kinases