Donelson J E, Murphy W J, Brentano S T, Rice-Ficht A C, Cain G D
J Cell Biochem. 1983;23(1-4):1-12. doi: 10.1002/jcb.240230102.
A recombinant clone of an expression-linked extra copy (ELC) gene of a trypanosome-variable surface glycoprotein was sequenced. In addition the sequences of the corresponding cDNA and portions of the two basic copy genes were determined. Comparison of these sequences reveals that the 5' boundary of the ELC-transposed segment (2.2 kb) occurs within a repetitive sequence about 700 bp upstream from the start codon of the coding sequence. This sequence does not contain internal symmetries and is not homologous with the repetitive sequence at the 3' boundary. The first 35 nucleotides of the cDNA are different than the corresponding ELC sequence and presumably were transcribed from another genomic location. A restriction fragment containing predominantly sequences outside of the 5' boundary hybridizes to a Pst I fragment whose length is variable in different trypanosome clones. This hybridization pattern is similar to that observed using probes for surface glycoprotein genes that are expressed via the nonduplication-associated (NDA) mechanism rather than the ELC mechanism. This indicates that there is a sequence correlation between these two DNA rearrangement mechanism.
对锥虫可变表面糖蛋白的表达连锁额外拷贝（ELC）基因的一个重组克隆进行了测序。此外，还测定了相应cDNA和两个基本拷贝基因部分的序列。这些序列的比较显示，ELC转座片段（2.2 kb）的5'边界出现在编码序列起始密码子上游约700 bp处的一个重复序列内。该序列不包含内部对称性，且与3'边界处的重复序列不同源。cDNA的前35个核苷酸与相应的ELC序列不同，推测是从另一个基因组位置转录而来的。一个主要包含5'边界以外序列的限制性片段与一个Pst I片段杂交，该片段的长度在不同的锥虫克隆中是可变的。这种杂交模式类似于使用针对通过非复制相关（NDA）机制而非ELC机制表达的表面糖蛋白基因的探针所观察到的模式。这表明这两种DNA重排机制之间存在序列相关性。
