The genes of major lysosomal membrane glycoproteins, lamp-1 and lamp-2. 5'-flanking sequence of lamp-2 gene and comparison of exon organization in two genes.
The genes of major lysosomal membrane glycoproteins, lamp-1 and lamp-2. 5'-flanking sequence of lamp-2 gene and comparison of exon organization in two genes.
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DOI：
10.1016/s0021-9258(18)31488-1
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发表时间：
1993-04
期刊：
影响因子：
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通讯作者：
R. Sawada;K. Jardine;M. Fukuda
中科院分区：
文献类型：
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作者：
R. Sawada;K. Jardine;M. Fukuda
人溶酶体膜糖蛋白lamp-1和lamp-2是存在于溶酶体膜中的主要唾液酸糖蛋白。lamp-2分子的表达受到独特的调节，而lamp-1是组成型合成的。为了研究lamp-2的独特表达，以及lamp-1和lamp-2的基因进化，我们分离了编码这些糖蛋白的基因组噬菌体克隆。基因组和cDNA序列的比较显示，灯-2基因由9个外显子。通过引物延伸分析确定lamp-2基因的转录起始位点。为了定位该基因的转录调控区，使用氯霉素乙酰转移酶作为报告分子测试5 '序列的各个区域的启动子活性。结果表明，5 ′侧翼序列从-172到-20碱基对具有较强的启动子活性。最值得注意的是，如果在所测试的5 '侧翼序列中包含5'上游的Kpn I重复序列，则启动子活性被抑制，从而表明Kpn I重复序列可能在lamp-2基因表达中具有某些调节功能。比较人lamp-2和lamp-1基因或鸡lamp-1基因的外显子结构，揭示这两种蛋白在相应的内含子中利用相同的外显子相位。此外，每个外显子编码几乎相同的蛋白质部分。另一方面，人lamp-1的氨基酸序列与其它物种的lamp-1的同源性高于其与人lamp-2的同源性。这些结果表明，lamp-1和lamp-2基因很可能是由原始基因的复制产生的，这发生在进化的早期。
Human lysosomal membrane glycoproteins lamp-1 and lamp-2 are the major sialoglycoproteins present in lysosomal membranes. The expression of lamp-2 molecules is uniquely regulated, whereas lamp-1 is constitutively synthesized. In order to investigate the unique expression of lamp-2, and the gene evolution of lamp-1 and lamp-2, we isolated genomic phage clones encoding these glycoproteins. Comparison of the genomic and cDNA sequences revealed that the lamp-2 gene consists of nine exons. The transcriptional start site of the lamp-2 gene was determined by primer extension analysis. In order to locate the transcriptional regulatory region of this gene, various regions of 5'-sequences were tested for promoter activity using chloramphenicol acetyltransferase as a reporter molecule. The results revealed that the 5'-flanking sequence from -172 to -20 base pairs has strong promoter activity. In this sequence, potential SP1 and AP-1 binding sites and CAAT boxes are found. Most notably, the promoter activity is suppressed if the 5' farther upstream KpnI repeat sequence is included in the tested 5'-flanking sequence, thus suggesting that the KpnI repeat sequence may have some regulatory function in the lamp-2 gene expression. Comparison of the exon organization of human lamp-2 and lamp-1 genes, or chicken lamp-1 gene, reveals that these two proteins utilize the same exon phase in corresponding introns. Furthermore, each exon encodes almost identical portions of the proteins. On the other hand, the amino acid sequence of human lamp-1 is more homologous to lamp-1 of other species than it is to human lamp-2. These results indicate that lamp-1 and lamp-2 genes were most likely produced by duplication of a primordial gene, which took place early in evolution.