Formation of a G-quadruplex at the BCL2 major breakpoint region of the t(14;18) translocation in follicular lymphoma.
The t(14;18) translocation in follicular lymphoma is one of the most common chromosomal translocations. Most breaks on chromosome 18 are located at the 3'-UTR of the BCL2 gene and are mainly clustered in the major breakpoint region (MBR). Recently, we found that the BCL2 MBR has a non-B DNA character in genomic DNA. Here, we show that single-stranded DNA modeled from the template strand of the BCL2 MBR, forms secondary structures that migrate faster on native PAGE in the presence of potassium, due to the formation of intramolecular G-quadruplexes. Circular dichroism shows evidence for a parallel orientation for G-quadruplex structures in the template strand of the BCL2 MBR. Mutagenesis and the DMS modification assay confirm the presence of three guanine tetrads in the structure. 1H nuclear magnetic resonance studies further confirm the formation of an intramolecular G-quadruplex and a representative model has been built based on all of the experimental evidence. We also provide data consistent with the possible formation of a G-quadruplex structure at the BCL2 MBR within mammalian cells. In summary, these important features could contribute to the single-stranded character at the BCL2 MBR, thereby contributing to chromosomal fragility.
Nambiar
Mridula
M
Department of Biochemistry, Indian Institute of Science, Bangalore-560 012, India.
Goldsmith
G
G
Moorthy
Balaji T
BT
Lieber
Michael R
MR
Joshi
Mamata V
MV
Choudhary
Bibha
B
Hosur
Ramakrishna V
RV
Raghavan
Sathees C
SC
D056905:Chromosome Breakpoints; D002883:Chromosomes, Human, Pair 14; D002887:Chromosomes, Human, Pair 18; D054856:G-Quadruplexes; D019254:Genes, bcl-2; D006801:Humans; D008224:Lymphoma, Follicular / Q000235:genetics*; D008958:Models, Molecular; D009154:Mutation; D019906:Nuclear Magnetic Resonance, Biomolecular; D013463:Sulfuric Acid Esters; D019914:Taq Polymerase; D014158:Transcription, Genetic; D014178:Translocation, Genetic
D013463:Sulfuric Acid Esters; D019914:Taq Polymerase; C007482:dimethyl sulfate