p51/p63 Controls Subunit α3 of the Major Epidermis Integrin Anchoring the Stem Cells to the Niche

Abstract

p51/p63, a member of the tumor suppressor p53 gene family, is crucial for skin development. We describe here identification of ITGA3 encoding integrin ␣ 3 as a target of its trans-activating function, proposing that p51/p63 allows epidermal stem cells to express laminin receptor ␣ 3 ␤ 1 for anchorage to the basement membrane. When activated by genotoxic stress or overexpressed ectopically in non-adherent cells, p51/p63 transduced a phenotype to attach to extracellular matrices, which was accompanied by expression of ITGA3. Motifs matching the p53-binding consensus sequence were located in a scattered form in intron 1 of human ITGA3, and served as p51/p63-responsive elements in reporter assays. In addition to the trans-activating ability of the TA isoform, we detected a positive effect of the ⌬N isoform on ITGA3. The high level ␣ 3 production in human keratinocyte stem cells diminished upon elimination of p51/p63 by small interfering RNA or by Ca 2؉ -induced differentiation. Furthermore, a chromatin immunoprecipitation experiment indicated a physical interaction of p51/p63 with intron 1 of ITGA3. This study provides a molecular basis for the standing hypothesis that p51/p63 is essential for epidermal-mesenchymal interactions.

p63(TP63) elicits strong trans-activation of the MFG-E8/lactadherin/BA46 gene through interactions between the TA and ΔN isoforms

“…MFG-E8 might affect these events during carcinoma tissue growth and/or wound healing, since no substantial defect appeared in the corresponding tissues of MFGE8-deficient mice. As reported recently, p63 induces membrane-anchored molecules including the integrin a 3 and b 4 subunits, envoplakin, Perp and bullous pemphigoid antigen-1/2 (Kurata et al, 2004;Ihrie et al, 2005;Osada et al, 2005a, b;Carroll et al, 2006) for cell-cell and cell-matrix binding. Soluble protein MFG-E8 may provide a novel mechanism of epithelialnonepithelial cell interactions around the p63-expressing cells.…”

“…The DN form mRNA became apparent after four additional PCR cycles. RT-PCR analyses for ITGA3 and MFGE8 (Kurata et al, 2004) suggested a relation between these mRNA levels and the p63 status. The MFGE8 mRNA level in HSC-1 and NHK is lower than that in FaDu, but is certainly (more than threefold) increased in comparison with the level in p63-negative HEK293.…”

“…PCR analyses indicated that the HS2/3 segment was significantly more abundant in the immunoprecipitate from the HA-TAp63g-expressing cells (Figure 6b) than in the precipitate from the control cells. The ITGA3 intron-1 segment having the p63 target sites (Kurata et al, 2004) also efficiently co-precipitated with HATAp63g, whereas the TATA box region of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) failed to do so. Control of nonimmune serum did not efficiently precipitate the HS2/3 segment (data not shown).…”

“…We obtained FaDu from American Type Culture Collection. Primary human neonatal keratinocyte culture was prepared as described by Kurata et al (2004).…”

“…With the oligomerization domain, DNp63 binds to TA-p63. Recent studies, however, detected positive effects of the DN isoforms upon certain promoters (Kurata et al, 2004;Wu et al, 2005;Helton et al, 2006).…”