Shurtleff S A, Meyers S, Hiebert S W, Raimondi S C, Head D R, Willman C L, Wolman S, Slovak M L, Carroll A J, Behm F
Department of Pathology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
Blood. 1995 Jun 15;85(12):3695-703.
Inv(16)(p13q22) is one of the most frequent chromosomal rearrangements found in acute myelogenous leukemia (AML), representing approximately 16% of documented karyotypic abnormalities. The inv(16) breakpoints have been cloned and shown to involve the non-DNA binding component of the AML-1 transcription factor complex termed core binding factor beta gene (CBF beta) on 16q and the smooth muscle myosin heavy chain gene (MYH11) on 16p. In this study, we analyzed 37 cases of inv(16)-containing AML and 4 cases with t(16;16)(p13;q22) for expression of the CBF beta/MYH11 chimeric message by reverse transcription-polymerase chain reaction (PCR) analysis. CBF beta/MYH11 chimeric messages were detected in 33 of 37 cases with the inv(16) and in the 4 t(16;16)-containing cases. Sequence analysis of PCR products showed extensive breakpoint heterogeneity in both CBF beta and MYH11. In addition to the previously described breakpoint in CBF beta at nucleotide (nt) 495 (amino acid 165), we have identified a second novel fusion point at nt 399 (amino acid 133) in 7% of the cases. Similarly, a unique breakpoint site was identified in MYH11 at nt 1098, as well as at three previously characterized sites at nts 994, 1201, and 1921. Of the 4 PCR-negative cases, 2 of 3 tested lacked CBF beta rearrangements by Southern blot analysis, suggesting the possible involvement of a different genomic locus in some cases with cytogenetic evidence of inv(16). To assess whether the portions of CBF-beta contained within the CBF beta/MYH11 chimeric products retain the ability to interact with their heterodimeric DNA-binding partner AML-1, we performed in vitro DNA-binding analysis. Recombinant CBF-beta polypeptides consisting of the N-terminal 165 amino acids retained their ability to interact with AML-1, whereas mutants containing only the N-terminal 133 amino acids interacted with AML-1 less efficiently. These data suggest that different CBF beta/MYH11 products may vary subtly in their biologic activities.
16号染色体倒位（inv(16)(p13q22)）是急性髓系白血病（AML）中最常见的染色体重排之一，约占已记录核型异常的16%。inv(16)的断点已被克隆，显示涉及16号染色体上AML-1转录因子复合体的非DNA结合成分，即核心结合因子β基因（CBFβ），以及16号染色体短臂上的平滑肌肌球蛋白重链基因（MYH11）。在本研究中，我们通过逆转录聚合酶链反应（PCR）分析，检测了37例含有inv(16)的AML病例和4例t(16;16)(p13;q22)病例中CBFβ/MYH11嵌合信息的表达。在37例inv(16)病例中的33例以及4例含有t(16;16)的病例中检测到了CBFβ/MYH11嵌合信息。PCR产物的序列分析显示，CBFβ和MYH11均存在广泛的断点异质性。除了之前描述的CBFβ在核苷酸（nt）495（氨基酸165）处的断点外，我们在7%的病例中还发现了一个位于nt 399（氨基酸133）的新融合点。同样，在MYH11中，在nt 1098处发现了一个独特的断点位点，以及在之前已确定的位于nts 994、1201和1921处的三个位点。在4例PCR阴性的病例中，通过Southern印迹分析，3例检测中有2例缺乏CBFβ重排，这表明在一些具有inv(16)细胞遗传学证据的病例中，可能涉及不同的基因组位点。为了评估CBFβ/MYH11嵌合产物中所含CBF-β部分是否保留了与其异二聚体DNA结合伴侣AML-1相互作用的能力，我们进行了体外DNA结合分析。由N端165个氨基酸组成的重组CBF-β多肽保留了与AML-1相互作用的能力，而仅含有N端133个氨基酸的突变体与AML-1的相互作用效率较低。这些数据表明，不同的CBFβ/MYH11产物在生物学活性上可能存在细微差异。
