Yang Y, Adam R D
Infectious Disease Section, Arizona Health Sciences Center, Tucson 85724.
Nucleic Acids Res. 1994 Jun 11;22(11):2102-8. doi: 10.1093/nar/22.11.2102.
The surfaces of Giardia lamblia trophozoites demonstrate variable expression of a set of cysteine-rich surface proteins, called variant-specific surface proteins (VSP). The cloned Giardia line, WBA6, expresses a 170 kD VSP (VSPA6 or CRP170) which contains approximately 18 to 23 copies of a 65 amino acid repeat. We have cloned the expressed vspA6 gene containing 23 repeats from a genomic library as well as copies of the vspA6 gene with only 8 or 9 repeats from both WBA6 and from WB1269, a cloned line derived from WBA6 which has lost the expressed copy of the gene. The recombinant clones containing the genes with only 8 or 9 repeats have 8 nucleotide substitutions in the coding region. All the recombinant clones map to the same chromosomal location, yet RNA sequencing and comparison with the transcript size indicate that only the clone with 23 repeats contains a gene producing a stable transcript. The most likely interpretation of these data is that G.lamblia trophozoites contain multiple alleles of the vspA6 gene of which only one is expressed.
蓝氏贾第鞭毛虫滋养体的表面表现出一组富含半胱氨酸的表面蛋白的可变表达，这些蛋白被称为变异特异性表面蛋白（VSP）。克隆的蓝氏贾第鞭毛虫株系WBA6表达一种170 kD的VSP（VSPA6或CRP170），其包含约18至23个65个氨基酸重复序列的拷贝。我们从基因组文库中克隆了含有23个重复序列的已表达vspA6基因，以及来自WBA6和WB1269（一个源自WBA6且已丢失该基因已表达拷贝的克隆株系）的仅含有8或9个重复序列的vspA6基因拷贝。含有仅8或9个重复序列基因的重组克隆在编码区有8个核苷酸取代。所有重组克隆都定位于相同的染色体位置，但RNA测序以及与转录本大小的比较表明，只有含有23个重复序列的克隆包含一个产生稳定转录本的基因。这些数据最可能的解释是，蓝氏贾第鞭毛虫滋养体含有vspA6基因的多个等位基因，其中只有一个被表达。
