Tsytsykova A V, Tsitsikov E N, Wright D A, Futcher B, Geha R S
Children's Hospital and Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA.
Mol Immunol. 1998 Nov;35(16):1057-67. doi: 10.1016/s0161-5890(98)00094-7.
The ubiquitin conjugating (ubc) E2 enzyme ubc-9 conjugates the ubiquitin-like peptide sentrin/SUMO-1/PIC1 to target proteins which include the Fas antigen. We show that the mouse genome contains four copies of the ubc-9 gene. These include a structural ubc-9 gene consisting of seven exons which encode a protein identical to human ubc-9, and three intronless processed pseudogenes. The open reading frames (ORF) of two of the pseudogenes, ubc9-psi1 and ubc9-psi2, correspond to the cDNA of ubc-9 and encode for proteins which differ from ubc9 by three and one amino acid substitutions respectively. The third pseudogene, ubc9-psi3, contains many mutations and stop codons. ubc9-psi1 and ubc9-psi2 are flanked by 5'- and 3'-untranslated (UT) regions homologous to those of the structural ubc-9 gene. Both genes contain a polyA tail and direct repeats at both ends suggesting that they arose by mRNA retroposition. Both ubc9-psi1 and ubc9-psi2 are transcribed into mRNA in murine cells. In contrast to ubc9, the protein products of ubc9-psil and ubc9-psi2 fail to bind Fas and to complement an yeast conditional ubc9 mutant. These results suggest that ubc9-psi1 and ubc9-psi2 encode for proteins that may interact with targets that differ from those recognized by ubc-9.
泛素缀合（ubc）E2酶ubc - 9将类泛素肽sentrin/SUMO - 1/PIC1缀合到包括Fas抗原在内的靶蛋白上。我们发现小鼠基因组包含四个ubc - 9基因拷贝。其中包括一个由七个外显子组成的结构ubc - 9基因，其编码的蛋白质与人类ubc - 9相同，以及三个无内含子的加工假基因。两个假基因ubc9 - psi1和ubc9 - psi2的开放阅读框（ORF）与ubc - 9的cDNA相对应，分别编码与ubc9有三个和一个氨基酸替换差异的蛋白质。第三个假基因ubc9 - psi3含有许多突变和终止密码子。ubc9 - psi1和ubc9 - psi2两侧是与结构ubc - 9基因同源的5'和3'非翻译（UT）区域。这两个基因都含有聚腺苷酸尾并且两端有直接重复序列，表明它们是通过mRNA逆转座产生的。ubc9 - psi1和ubc9 - psi2在小鼠细胞中都转录成mRNA。与ubc9不同，ubc9 - psil和ubc9 - psi2的蛋白质产物不能结合Fas，也不能互补酵母条件性ubc9突变体。这些结果表明ubc9 - psi1和ubc9 - psi2编码的蛋白质可能与ubc - 9识别的靶标不同的靶标相互作用。
