p63(TP63) elicits strong trans-activation of the MFG-E8/lactadherin/BA46 gene through interactions between the TA and DeltaN isoforms.
We report here that human MFGE8 encoding milk fat globule-EGF factor 8 protein (MFG-E8), also termed 46 kDa breast epithelial antigen and lactadherin, is transcriptionally activated by p63, or TP63, a p53 (TP53) family protein frequently overexpressed in head-and-neck squamous cell carcinomas, mammary carcinomas and so on. Despite that human MFG-E8 was originally identified as a breast cancer marker, and has recently been reported to provide peptides for cancer immunotherapy, its transcriptional control remains an open question. Observations in immunohistochemical analyses, a tetracycline-induced p63 expression system and keratinocyte cultures suggested a physiological link between p63 and MFGE8. By reporter assays with immediately upstream regions of MFGE8, we determined that the trans-activator (TA) isoforms of p63 activate MFGE8 transcription though a p53/p63 motif at -370, which was confirmed by a chromatin immunoprecipitation experiment. Upon siRNA-mediated p63 silencing in a squamous cell carcinoma line, MFG-E8 production decreased to diminish Saos-2 cell adhesion. Interestingly, the DeltaN-p63 isoform lacking the TA domain enhanced the MFGE8-activating function of TA-p63, if DeltaN-p63 was dominant over TA-p63 as typically observed in undifferentiated keratinocytes and squamous cell carcinomas, implying a self-regulatory mechanism of p63 by the TA:DeltaN association. MFG-E8 may provide a novel pathway of epithelial-nonepithelial cell interactions inducible by p63, probably in pathological processes.
Okuyama
T
T
Ikawa Laboratory, RIKEN, Wako, Japan.
Kurata
S
S
Tomimori
Y
Y
Fukunishi
N
N
Sato
S
S
Osada
M
M
Tsukinoki
K
K
Jin
H-F
HF
Yamashita
A
A
Ito
M
M
Kobayashi
S
S
Hata
R-I
RI
Ikawa
Y
Y
Katoh
I
I
D000954:Antigens, Surface / Q000235:genetics*; D001483:Base Sequence; D002277:Carcinoma / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008894:Milk Proteins / Q000235:genetics*; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D015534:Trans-Activators / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors; D015533:Transcriptional Activation; D025521:Tumor Suppressor Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
D000954:Antigens, Surface; D004268:DNA-Binding Proteins; C098942:MFGE8 protein, human; D008894:Milk Proteins; D020033:Protein Isoforms; D034741:RNA, Small Interfering; C115051:TP63 protein, human; D015534:Trans-Activators; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins