DNA structural properties of AF9 are similar to MLL and could act as recombination hot spots resulting in MLL/AF9 translocations and leukemogenesis.
The human AF9 gene at 9p22 is one of the most common fusion partner genes with the MLL gene at 11q23, resulting in the t(9;11)(p22;q23). The MLL-AF9 fusion gene is associated with de novo acute myelo-genous leukemia (AML), rarely with acute lymphocytic leukemia (ALL) and with therapy related leukemia (t-AML). The AF9 gene is >100 kb and two patient breakpoint cluster regions (BCRs) have been identified; BCR1 is within intron 4, previously called site A, whereas BCR2 or site B spans introns 7 and 8. Patient breakpoint locations were determined previously by RT-PCR and by genomic DNA cloning. In this study, we defined the exon-intron boundaries and identified several different structural elements in AF9 including a co-localizing in vivo DNA topo II cleavage site and an in vitro DNase I hypersensitive (DNase 1 HS) site in intron 7 in BCR2. Reversibility experiments demonstrated a religation of the topo II cleavage sites. The location of the in vivo topo II cleavage site was confirmed in vitro using a topo II cleavage assay. In addition, two scaffold associated regions (SARs) are located centromeric to the topo II and DNase I HS cleavage sites and border both patient breakpoint regions: SAR1 is located in intron 4, whereas SAR2 encompasses parts of exons 5-7. This study demonstrates that the patient breakpoint regions of AF9 share the same structural elements as the MLL BCR. We describe a DNA breakage and repair model for non-homologous recombination between MLL and its partner genes, particularly AF9.
Strissel
P L
PL
University of Chicago Department of Medicine, Section of Hematology Oncology, Chicago, IL 60637-1470, USA. pstrisse@medicine.bsd.uchicago.edu
Strick
R
R
Tomek
R J
RJ
Roe
B A
BA
Rowley
J D
JD
Zeleznik-Le
N J
NJ
D001665:Binding Sites; D002460:Cell Line; D002843:Chromatin / Q000235:genetics; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D004273:DNA, Neoplasm / Q000737:chemistry / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics*; D003850:Deoxyribonuclease I / Q000378:metabolism; D011495:Histone-Lysine N-Methyltransferase; D006801:Humans; D007438:Introns; D019169:Jurkat Cells; D020014:K562 Cells; D007938:Leukemia / Q000235:genetics*; D008969:Molecular Sequence Data; D051788:Myeloid-Lymphoid Leukemia Protein; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D015514:Oncogene Proteins, Fusion / Q000235:genetics*; D011519:Proto-Oncogenes; D011995:Recombination, Genetic; D017422:Sequence Analysis, DNA; D014157:Transcription Factors; D014178:Translocation, Genetic; D014407:Tumor Cells, Cultured
D002843:Chromatin; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; C497422:KMT2A protein, human; C489901:MLLT3 protein, human; D009687:Nuclear Proteins; D015514:Oncogene Proteins, Fusion; D014157:Transcription Factors; D051788:Myeloid-Lymphoid Leukemia Protein; D011495:Histone-Lysine N-Methyltransferase; D003850:Deoxyribonuclease I; D004250:DNA Topoisomerases, Type II