Tissue-specific regulation of Apaf-1 expression by p53.
The p53 tumor suppressor is a transcription factor that regulates cell cycle and apoptosis in response to a variety of environmental stress conditions. Recent studies indicated that the apoptotic protease activating factor-1 (Apaf-1) is a direct transcriptional target of p53 in DNA damage-induced apoptosis. However, the dependence of Apaf-1 expression on p53 has not been shown in normal physiological conditions. To further investigate their relationship, we first examined Apaf-1 protein levels in seven organs including brain, heart, kidney, liver, lung, spleen, and testis of wild-type (p53+/+) and p53-deficent (p53-/-) mice by Western blot analysis. The heart and spleen of the p53-/- mice showed a reduced Apaf-1 protein expression compared with the p53+/+ controls, while other organs did not show significant difference. The results from Western blot analysis were further confirmed by immunohistochemistry. Semi-quantitative RT-PCR was then employed to determine the expression of Apaf-1 transcripts. Similarly, we detected a lower Apaf-1 mRNA level in the heart and spleen of p53-/- mice compared with the p53+/+ controls, supporting a transcriptional upregulation of Apaf-1 by p53. Taken together, these results demonstrate that p53 regulation of Apaf-1 expression is tissue-specific.
Ho
Clement K
CK
Department of Medicine, Division of Dermatology, Vancouver Hospital and Health Sciences Centre, University of British Columbia, Vancouver, BC, V6H 3Z6, Canada.
Bush
Jason A
JA
Li
Gang
G
D000818:Animals; D017209:Apoptosis; D053477:Apoptotic Protease-Activating Factor 1; D015153:Blotting, Western; D005786:Gene Expression Regulation; D007150:Immunohistochemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009206:Myocardium / Q000378:metabolism; D014176:Protein Biosynthesis; D011506:Proteins; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013154:Spleen / Q000378:metabolism; D014018:Tissue Distribution; D014158:Transcription, Genetic; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis*; D015854:Up-Regulation
C506593:Apaf1 protein, mouse; D053477:Apoptotic Protease-Activating Factor 1; D011506:Proteins; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53