Ord T, Kolmer M, Villems R, Saarma M
Institute of Chemical Physics and Biophysics, Estonian Academy of Sciences, U.S.S.R.
Gene. 1990 Jul 16;91(2):241-6. doi: 10.1016/0378-1119(90)90094-8.
Two human genomic libraries were probed with bovine prochymosin (bPC) cDNA. Recombinant clones covering a genomic region homologous to the entire coding region and flanking sequences of the bPC gene were isolated. Human sequences homologous to exons of the bPC gene are distributed in a DNA fragment of 10 kb. Alignment of the human sequences and the exons of bPC reveals that the human 'exons' 1-3, 5 and 7-9 have sizes identical to the corresponding bovine exons, but a nucleotide (nt) has been deleted in the human exon 4 and two nt in the human exon 6. The aligned human sequence and the coding part of bPC gene share 82% nt homology, the value ranging, in separate exons, from 76 (exon 1) to 84% (exons 5 and 6). 150 bp of 5'-flanking sequence of the human gene has 75% homology to the corresponding region of bPC gene and contains a TATA-box in a similar position. A 1-nt deletion in the human exon 4 would shift the translational reading frame of a putative human PC mRNA relative to bPC mRNA, and result in an in-phase terminator spanning codons 163 and 164 in bPC mRNA. Another terminator in-phase with the amino-acid sequence encoded by the bPC gene occurs in the human exon 5 and the second frameshift mutation in exon 6. Thus, the nt sequence analysis of the human genomic region has revealed the presence of mutations that have rendered it unable to produce a full-length protein homologous to bPC and, therefore, we refer to this gene as a human prochymosin pseudogene (hPC psi). Blot-hybridization analysis of human genomic DNA indicates that hPC psi is a single gene in the human genome.
用牛凝乳酶原（bPC）cDNA对两个人类基因组文库进行探测。分离出了覆盖与bPC基因整个编码区及侧翼序列同源的基因组区域的重组克隆。与bPC基因外显子同源的人类序列分布在一个10 kb的DNA片段中。人类序列与bPC外显子的比对显示，人类“外显子”1 - 3、5和7 - 9的大小与相应的牛外显子相同，但人类外显子4中缺失了一个核苷酸（nt），人类外显子6中缺失了两个nt。比对后的人类序列与bPC基因的编码部分具有82%的核苷酸同源性，在各个外显子中，该值范围从76%（外显子1）到84%（外显子5和6）。人类基因5' - 侧翼序列的150 bp与bPC基因的相应区域具有75%的同源性，并且在相似位置含有一个TATA框。人类外显子4中的一个nt缺失会使假定的人类PC mRNA相对于bPC mRNA的翻译阅读框发生移位，并导致在bPC mRNA中跨越密码子163和164的同相位终止子。另一个与bPC基因编码的氨基酸序列同相位的终止子出现在人类外显子5中，外显子6中存在第二个移码突变。因此，对人类基因组区域的核苷酸序列分析揭示了存在一些突变，这些突变使其无法产生与bPC同源的全长蛋白质，所以，我们将该基因称为人类凝乳酶原假基因（hPC psi）。对人类基因组DNA的印迹杂交分析表明，hPC psi在人类基因组中是一个单基因。
