Ting J P, Carrington M N, Salter R D, DeMars R, Cresswell P
Immunogenetics. 1985;22(6):571-83. doi: 10.1007/BF00430305.
We examined the possibility that one mechanism for controlling HLA-DR alpha gene expression involves the alteration of chromatin structure. Chromatin structure was analyzed by measuring the susceptibility of DR alpha genes in intact nuclei to nuclease treatment. We first examined a somatic cell hybrid of a T-lymphoblastoid cell line (LCL) and a B-LCL, since the DR alpha gene, which is inactive in the T-LCL parent, is expressed in the hybrid, thus providing a system to study DR alpha gene induction. The hybrid line 174 X CEM.T1 contains and expresses solely the DR alpha gene from the T-LCL parent, since the DR alpha gene from the B-LCL parent, 174, is deleted. Using cytoplasmic dot blot analysis and RNA-DNA Northern hybridization, we detected DR alpha-specific transcripts in the hybrid, but not in the parental lines, indicating activation of the DR alpha gene in the hybrid. The transcribed DR alpha gene from the hybrid was compared with the untranscribed gene from the T-LCL parental line, and an association between DR alpha gene expression and increased sensitivity to DNase I was observed. A switch in the chromatin structure of the DR alpha gene from a closed to an open configuration apparently occurred in this hybrid. Such a change is associated with DR alpha gene expression. Comparison of a DR-positive B-LCL and an isogenic DR-negative T-LCL also showed that the chromatin of the former is more sensitive to DNase I digestion. There were no restriction enzyme fragment length differences between the DR alpha genes from 174 X CEM.T1 and CEMR, indicating that the process of somatic cell hybridization did not result in DNA rearrangement or translocation.
我们研究了控制HLA - DRα基因表达的一种机制可能涉及染色质结构改变的可能性。通过测量完整细胞核中DRα基因对核酸酶处理的敏感性来分析染色质结构。我们首先检测了一个T淋巴细胞样细胞系（LCL）和一个B - LCL的体细胞杂种，因为在T - LCL亲本中无活性的DRα基因在杂种中表达，从而提供了一个研究DRα基因诱导的系统。杂种细胞系174 X CEM.T1仅包含并表达来自T - LCL亲本的DRα基因，因为来自B - LCL亲本174的DRα基因被删除。通过细胞质斑点印迹分析和RNA - DNA Northern杂交，我们在杂种中检测到了DRα特异性转录本，但在亲本细胞系中未检测到，这表明杂种中DRα基因被激活。将杂种中转录的DRα基因与T - LCL亲本细胞系中未转录的基因进行比较，观察到DRα基因表达与对DNase I敏感性增加之间存在关联。在这个杂种中，DRα基因的染色质结构显然从封闭构型转变为开放构型。这种变化与DRα基因表达相关。对一个DR阳性的B - LCL和一个同基因DR阴性的T - LCL的比较也表明，前者的染色质对DNase I消化更敏感。174 X CEM.T1和CEMR的DRα基因之间没有限制性酶切片段长度差异，这表明体细胞杂交过程未导致DNA重排或易位。
