Panhandle and reverse-panhandle PCR enable cloning of der(11) and der(other) genomic breakpoint junctions of MLL translocations and identify complex translocation of MLL, AF-4, and CDK6.
We used panhandle PCR to clone the der(11) genomic breakpoint junction in three leukemias with t(4;11) and devised reverse-panhandle PCR to clone the breakpoint junction of the other derivative chromosome. This work contributes two elements to knowledge on MLL translocations. First is reverse-panhandle PCR for cloning breakpoint junctions of the other derivative chromosomes, sequences of which are germane to understanding the MLL translocation process. The technique revealed duplicated sequences in one case of infant acute lymphoblastic leukemia (ALL) and small deletions in a case of treatment-related ALL. The second element is discovery of a three-way rearrangement of MLL, AF-4, and CDK6 in another case of infant ALL. Cytogenetic analysis was unsuccessful at diagnosis, but suggested t(4;11) and del(7)(q21q31) at relapse. Panhandle PCR analysis of the diagnostic marrow identified a breakpoint junction of MLL intron 8 and AF-4 intron 3. Reverse-panhandle PCR identified a breakpoint junction of CDK6 from band 7q21-q22 and MLL intron 9. CDK6 encodes a critical cell cycle regulator and is the first gene of this type disrupted by MLL translocation. Cdk6 is overexpressed or disrupted by translocation in many cancers. The in-frame CDK6-MLL transcript is provocative with respect to a potential contribution of the predicted Cdk6-MLL fusion protein in the genesis of the ALL, which also contains an in-frame MLL-AF4 transcript. The sequences in these three cases show additional MLL genomic breakpoint heterogeneity. Each breakpoint junction suggests nonhomologous end joining and is consistent with DNA damage and repair. CDK6-MLL is a new fusion of both genes.
Raffini
Leslie J
LJ
Division of Oncology, Joseph Stokes, Jr. Research Institute, Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA.
Slater
Diana J
DJ
Rappaport
Eric F
EF
Lo Nigro
Luca
L
Cheung
Nai-Kong V
NK
Biegel
Jaclyn A
JA
Nowell
Peter C
PC
Lange
Beverly J
BJ
Felix
Carolyn A
CA
D001483:Base Sequence; D002880:Chromosomes, Human, Pair 11; D002894:Chromosomes, Human, Pair 4; D003001:Cloning, Molecular; D051361:Cyclin-Dependent Kinase 6; D018844:Cyclin-Dependent Kinases; D004268:DNA-Binding Proteins / Q000235:genetics*; D005260:Female; D015321:Gene Rearrangement; D011495:Histone-Lysine N-Methyltransferase; D006801:Humans; D008969:Molecular Sequence Data; D051788:Myeloid-Lymphoid Leukemia Protein; D009687:Nuclear Proteins / Q000235:genetics*; D016133:Polymerase Chain Reaction / Q000379:methods*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D011519:Proto-Oncogenes; D014157:Transcription Factors; D035602:Transcriptional Elongation Factors; D014178:Translocation, Genetic
D004268:DNA-Binding Proteins; C497422:KMT2A protein, human; D009687:Nuclear Proteins; D014157:Transcription Factors; D035602:Transcriptional Elongation Factors; D051788:Myeloid-Lymphoid Leukemia Protein; C081449:AFF1 protein, human; D011495:Histone-Lysine N-Methyltransferase; D017346:Protein Serine-Threonine Kinases; C495911:CDK6 protein, human; D051361:Cyclin-Dependent Kinase 6; D018844:Cyclin-Dependent Kinases