Zhang J G, Goldman J M, Cross N C
LRF Leukaemia Unit, Royal Postgraduate Medical School, Hammersmith Hospital, London.
Br J Haematol. 1995 May;90(1):138-46. doi: 10.1111/j.1365-2141.1995.tb03392.x.
In order to understand better the mechanism of translocation between the BCR and ABL genes in CML, we have exploited a 'bubble PCR' technique to clone genomic breakpoints. BCR-ABL junction fragments were successfully amplified and sequenced in 14/32 (43%) patients tested. Breakpoints were dispersed throughout the major breakpoint cluster region without any clustering or hot spots. In three cases Alu sequences were found at or near the breakpoint on the ABL side of the translocation but no other obvious sequence homologies were found either in BCR or ABL. The translocation event was characterized further in three other patients by amplifying the reciprocal ABL-BCR junction on the 9q+ chromosome and also normal ABL around breakpoints. In two of these patients a few nucleotides of BCR and ABL were either duplicated or deleted on translocation, suggesting that staggered cuts had been made in the DNA strand prior to recombination. In the third patient 50 bp of ABL was deleted and 159 bp of M-BCR including exon b3 was duplicated, indicating either that the single-stranded cuts may span a larger distance than previously thought or that another mechanism, perhaps involving gene conversion, may be involved in this instance.
为了更好地理解慢性粒细胞白血病（CML）中BCR和ABL基因之间易位的机制，我们采用了“气泡PCR”技术来克隆基因组断点。在32例接受检测的患者中，有14例（43%）成功扩增并测序了BCR-ABL连接片段。断点分散在主要断点簇区域，没有任何聚集或热点。在3例病例中，在易位ABL一侧的断点处或其附近发现了Alu序列，但在BCR或ABL中未发现其他明显的序列同源性。通过扩增9q+染色体上相互的ABL-BCR连接以及断点周围的正常ABL，对另外3例患者的易位事件进行了进一步表征。在其中2例患者中，易位时BCR和ABL的几个核苷酸发生了重复或缺失，这表明在重组之前DNA链上进行了交错切割。在第3例患者中，ABL缺失了50 bp，包括外显子b3的M-BCR的159 bp发生了重复，这表明单链切割可能跨越比以前认为的更大的距离，或者在这种情况下可能涉及另一种机制，也许涉及基因转换。
