Physiological function of proprotein convertase PACE4

PACE 4（成对碱性氨基酸裂解酶）是哺乳动物kexin样前蛋白转化酶家族的成员，其含有枯草杆菌蛋白酶样催化结构域。为了确定这些异构体的来源，整个人PACE 4基因被分离为一组重叠的基因组DNA片段，并通过限制性内切酶消化和核苷酸序列测定进行分析。人PACE 4基因跨越至少250 kb，分布在25个外显子上，范围从39到1，422个碱基对。人PACE 4基因是迄今为止报道的最大的kexin样前蛋白转化酶基因。其基因组结构最显着的特征是内含子的大小和外显子的数量，尽管该家族中保守的信号肽、前肽和催化结构域的一般组织与其他kexin报道的非常相似-样蛋白酶基因。PACE 4基因组DNA的结构分析表明，多种PACE 4转录物是作为选择性RNA剪接事件的结果产生的，包括外显子跳跃，以及内部5 '剪接供体和多聚腺苷酸化位点的使用差异。通过引物延伸分析，在ATG翻译起始位点上游314 bp处检测到一个主要的转录起始位点。对PACE 4基因5 '侧翼区的序列分析表明，在起始位点的近端上游区域缺少TATA和CCAAT盒，尽管存在几种转录因子的潜在结合位点，包括SP 1、AP 1、AP 2、PEA 3、Ets-1、GHF（生长激素因子）-1、CREB（环AMP反应元件结合蛋白）和碱性螺旋-环-螺旋蛋白。在5-侧翼区发现了一个不寻常的序列的六个串联重复的十九聚体（GGCCTGGGGGTTCACCTGC）含有一个E盒。这些结果表明，PACE 4不是组成型基因产物，其表达受多种转录因子调控。

PACE4 (paired basic amino acid cleaving enzyme) is a member of a family of the mammalian kexin-like proprotein convertases containing a subtilisin-like catalytic domain. To determine the origin of these isoforms, the entire human PACE4 gene Las been isolated as a set of overlapping genomic DNA fragments, and analyzed by restriction enzyme digestion and nucleotide sequence determination. The human PACE4 gene spans at least 250 kb and is distributed over 25 exons that range in e from 39 to 1,422 base pairs. Human PACE4 gene is the largest kexin-like proprotein convertase gene reported to date. The most striking feature of its genomic structure is the size of the introns and the number of exons, although the general organization of signal peptide, propeptide, and catalytic domains, which are conserved in this family, is very similar to that reported for other kexin-like protease genes. The structural analysis of PACE4 genomic DNA indicates that multiple PACE4 transcripts are produced as a consequence of alternative RNA splicing events, including exon skipping, and differences in the usage of the inner 5'-splicing donor and polyadenylation sites. A major transcriptional start site was detected 314 bp upstream from the ATG translational start site by primer extension analysis. Sequence analysis of the 5'-flanking region revealed that PACE4 gene lacks TATA and CCAAT boxes in the proximal upstream region of the start site, although potential binding sites for several transcription factors including SP1, AP1, AP2, PEA3, Ets-1, GHF(growth hormone factor)-1, CREB(cyclic AMP response element binding protein), and basic helix-loop-helix proteins, were present. An unusual sequence of six tandem repeats of a nonadecamer (GGCCTGGGGGTTCACCTGC) containing an E box is found in the 5-flanking region. These results suggest that PACE4 is not a constitutive gene product and its expression is regulated by various transcription factors.