TY - JOUR
T1 - Caspases mediate retinoic acid-induced degradation of the acute promyelocytic leukemia PML/RARα fusion protein
AU - Nervi, Clara
AU - Ferrara, Fabiana F.
AU - Fanelli, Mirco
AU - Rippo, Maria Rita
AU - Tomassini, Barbara
AU - Ferrucci, Pier Francesco
AU - Ruthardt, Martin
AU - Gelmetti, Vania
AU - Gambacorti-Passerini, Carlo
AU - Diverio, Daniela
AU - Grignani, Francesco
AU - Pelicci, Pier Giuseppe
AU - Testi, Roberto
PY - 1998/10/1
Y1 - 1998/10/1
N2 - All-trans-retinoic acid (RA) treatment induces morphological remission in acute promyelocytic leukemia (APL) patients carrying the t(15;17) and expressing the PML/RARα product by inducing terminal differentiation of the leukemic clone. RA treatment induces downregulation of PML/RARα and reorganization of the PML-nuclear bodies. These events have been proposed to be essential for the induction of APL cell differentiation by RA. Here, we show that in the APL* derived NB4 cell line as well as in myeloid precursor U937 cells expressing the PML/RARα (U937/PR9) and in blasts from APL patients, the PML/RARα fusion protein is cleaved by a caspase 3-like activity induced by RA treatment. In fact, a caspase 3-like activity is detectable in PML/RARα expressing cells after RA treatment, and selective caspase inhibitor peptides are able to prevent the RA-induced degradation of the fusion protein in vivo and in vitro. Using recombinant caspases and PML/RARα deletion mutants we mapped a caspase 3 cleavage site (Asp 522) within the α-helix region of the PML component of the fusion protein. The extent of PML/RARα cleavage directly correlates with the ability of RA to restore the normal PML nuclear bodies (NBs) pattern. However, RA-induced differentiation is not prevented by the persistence of the fusion product and occurs in the absence of normally structured PML NBs. These results indicate that PML/RARα is directly involved in conferring RA sensitivity of APL cells and that the RA-induced reassembly of PML NBs is the consequence of the disappearance of PML/RARα.
AB - All-trans-retinoic acid (RA) treatment induces morphological remission in acute promyelocytic leukemia (APL) patients carrying the t(15;17) and expressing the PML/RARα product by inducing terminal differentiation of the leukemic clone. RA treatment induces downregulation of PML/RARα and reorganization of the PML-nuclear bodies. These events have been proposed to be essential for the induction of APL cell differentiation by RA. Here, we show that in the APL* derived NB4 cell line as well as in myeloid precursor U937 cells expressing the PML/RARα (U937/PR9) and in blasts from APL patients, the PML/RARα fusion protein is cleaved by a caspase 3-like activity induced by RA treatment. In fact, a caspase 3-like activity is detectable in PML/RARα expressing cells after RA treatment, and selective caspase inhibitor peptides are able to prevent the RA-induced degradation of the fusion protein in vivo and in vitro. Using recombinant caspases and PML/RARα deletion mutants we mapped a caspase 3 cleavage site (Asp 522) within the α-helix region of the PML component of the fusion protein. The extent of PML/RARα cleavage directly correlates with the ability of RA to restore the normal PML nuclear bodies (NBs) pattern. However, RA-induced differentiation is not prevented by the persistence of the fusion product and occurs in the absence of normally structured PML NBs. These results indicate that PML/RARα is directly involved in conferring RA sensitivity of APL cells and that the RA-induced reassembly of PML NBs is the consequence of the disappearance of PML/RARα.
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M3 - Article
C2 - 9746761
AN - SCOPUS:0032188989
VL - 92
SP - 2244
EP - 2251
JO - Blood
JF - Blood
SN - 0006-4971
IS - 7
ER -