Molecular cloning and DNA sequence of a Dictyostelium cDNA encoding a Ran/TC4 related GTP binding protein belonging to the ras superfamily.
Molecular cloning and DNA sequence of a Dictyostelium cDNA encoding a Ran/TC4 related GTP binding protein belonging to the ras superfamily.
复制标题
编码属于 ras 超家族的 Ran/TC4 相关 GTP 结合蛋白的盘基网柄菌 cDNA 的分子克隆和 DNA 序列。
DOI：
10.1093/nar/21.7.1675
复制
发表时间：
1993
影响因子：
14.9
通讯作者：
Cardelli,J
中科院分区：
文献类型：
--
作者：
Bush,J;Cardelli,J
人类基因TC 4/ran（在酵母中也称为spi）编码属于ras超家族的小分子量GT α（1，2，3，4）。与ras超家族的其他成员不同，其在细胞质中发挥各种作用，包括调节肌动蛋白细胞骨架，控制囊泡运输和细胞增殖，Ran被假设在细胞核中起作用。Ran通过其与RCC 1蛋白的结合而与基因组DNA结合（5），并且Ran的突变形式的表达阻断DNA复制（6）。这些结果表明，Ran在DNA代谢中起着直接的作用，并可能将DNA合成的完成与有丝分裂的开始偶联。在饥饿时，生长的盘基网柄藻细胞进入发育周期，其最终形成基本上两种细胞类型，孢子细胞和柄细胞（7）。成为柄细胞或孢子细胞的决定部分取决于细胞在细胞周期中饥饿时所处的位置（8）。因此，细胞周期的调节可以深刻地影响阿米巴虫未来的分化途径。（Dict TC4，Genbank登录号L09720）在λ gtIII cDNA文库的筛选期间分离（用来自4小时发育细胞的poly A+ RNA制备），使用编码非常保守的氨基酸序列（DTAGQE）的寡核苷酸在属于ras超家族的所有GTP酶中发现。对804个核苷酸的cDNA插入片段在两条链上进行测序，发现其含有一个单一的长开放阅读框，起始于核苷酸位置27-29的ATG，终止于位置663-665的TAA终止密码子。预测的212个氨基酸的蛋白质产物在全长上显示出与Spi和TC 4蛋白在氨基酸水平上的显著同源性（69%同一性，图1），尽管Spi和TC 4在同源性上彼此更接近（80%同一性）并且两者都是216个氨基酸长。然而，在已知对GTP结合重要的所有区域中，网骨藻T-C4样蛋白与这些其他GTP酶几乎相同（图1中的框区）。此外，所有三种蛋白质在羧基末端区域含有高百分比的酸性氨基酸残基。Northernblot分析（结果未显示）表明，黏菌TC 4基因在生长细胞中以相对高的水平表达，但在发育后期以大大降低的水平表达。
The human gene TC4/ran (also called spi in yeast) codes for a small molecular weight GTPase belonging to the ras superfamily (1, 2, 3, 4). Unlike other members of the ras superfamily which play a variety of roles in the cytoplasm including the regulation of the actin cytoskeleton, and control of vesicular traffic and cell proliferation, Ran is hypothesized to function in the nucleus. Ran is bound to genomic DNA through its association with the RCC1 protein (5) and expression of a mutant form of Ran blocks DNA replication (6). These results suggest that Ran plays a direct role in DNA metabolism and may couple the completion of DNA synthesis to the onset of mitosis. Upon starvation, growing Dictyostelium discoideum cells enter a developmental cycle which culminates in the formation of basically two cell types, spore cells and stalk cells (7). The decision to become a stalk or spore cell is determined in part by the position in the cell cycle the cell happens to be when starved (8). Thus, regulation of the cell cycle can profoundly influence the future differentiation pathways followed by the amoebae.The apparent Dictyostelium homologue to the TC4 and spi genes (Dict TC4, Genbank accession number L09720) was isolated during a screen of a lambda gtIll cDNA library (prepared with poly A+ RNA from 4 hour developing cells) using an oligonucleotide codingfor a very conserved amino acid sequence (DTAGQE) found in all GTPases belonging to the ras superfamily. The cDNA insert of 804 nucleotides was sequenced on both strands andfound to contain a single long open reading frame beginning with an ATG at nucleotide positions 27-29 and ending with a TAA stop codon at position 663-665. The predicted protein product of 212 amino acids showed significant homology at the amino acid level to bothSpi and TC4 proteins over the full length (69% identity, Figure 1), although Spi and TC4 were closer to each other in homology (80% identity) and both were 216 amino acid long. However, the Dictyostelium T-C4-like protein was nearly identical to these other GTPases in all theregions known to be important in GTP binding (boxed regions in Figure 1). In addition, all three proteins contained a high percentage of acidic amino acid residues in the carboxy terminal regions. Northernblot analysis (results not shown) indicated that the slime mold TC4 gene was expressed at relatively high levels in growing cells but at greatly reduced levels late in development.