ETV6/RUNX1 abrogates mitotic checkpoint function and targets its key player MAD2L1.
Approximately 25% of childhood B-cell precursor acute lymphoblastic leukemia have an ETV6/RUNX1 (E/R) gene fusion that results from a t(12;21). This genetic subgroup of leukemia is associated with near-triploidy, near-tetraploidy, and trisomy 21 as rather specific types of secondary changes. Here, we show that, unlike various controls, E/R-expressing Ba/F3 clones acquire a tetraploid karyotype on prolonged culture, corroborating the assumption that E/R may attenuate the mitotic checkpoint (MC). Consistent with this notion, E/R-expressing diploid murine and human cell lines have decreased proportions of cells with 4N DNA content and a lower mitotic index when treated with spindle toxins. Moreover, both RUNX1 and E/R regulate mitotic arrest-deficient 2 L1 (MAD2L1), an essential MC component, by binding to promoter-inherent RUNX1 sites, which results in down-regulation of MAD2L1 mRNA and protein in E/R-expressing cells. Forced expression of E/R also abolishes RUNX1-induced reporter activation, whereas E/R with a mutant DNA-binding site leads to only minor effects. Our data link for the first time E/R, MC, and MAD2L1 and provide new insights into the function of the E/R fusion gene product. Although tetraploidy is an almost exclusive feature of E/R-positive leukemias, its rarity within this particular subgroup implies that further yet unknown factors are required for its manifestation.
Krapf
G
G
Children's Cancer Research Institute, Vienna, Austria.
Kaindl
U
U
Kilbey
A
A
Fuka
G
G
Inthal
A
A
Joas
R
R
Mann
G
G
Neil
J C
JC
Haas
O A
OA
Panzer-Grümayer
E R
ER
D002135:Calcium-Binding Proteins / Q000235:genetics*; D018797:Cell Cycle Proteins / Q000235:genetics*; D045744:Cell Line, Tumor; D050676:Core Binding Factor Alpha 2 Subunit; D050939:Gene Fusion; D015321:Gene Rearrangement; D006801:Humans; D007621:Karyotyping; D064246:Mad2 Proteins; D008938:Mitosis / Q000235:genetics*; D015514:Oncogene Proteins, Fusion / Q000235:genetics*; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000235:genetics*; D000097764:ETS Translocation Variant 6 Protein
D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; D050676:Core Binding Factor Alpha 2 Subunit; D064246:Mad2 Proteins; D015514:Oncogene Proteins, Fusion; D012097:Repressor Proteins; C577697:MAD2L1 protein, human; C102421:TEL-AML1 fusion protein; D000097764:ETS Translocation Variant 6 Protein