Romans P, Firtel R A
J Mol Biol. 1985 Jun 5;183(3):311-26. doi: 10.1016/0022-2836(85)90003-8.
Sequences flanking the protein-coding regions of 15 of the 17 to 20 actin genes in the cellular slime mold Dictyostelium discoidium have been determined. Comparison of sequences among genes shows that they contain extensive homologies at both the 5' and 3' ends of the coding regions. On the basis of these homologies, actin genes fall into three groups. Group I consists of Actin 8 alone. Group II consists of the two closely linked genes Actin 3-sub1 and Actin 3-sub2. These two genes differ from all other actin genes in the location of their TATA box and oligo(dT) run, and diverge substantially in their coding sequence as well. Group III contains all the rest of the genes we have studied. Within this group, there are two subgroups of genes, IIIA (Actins 5, 9 and 10) and IIIB (Actins M6, 2-sub1 and 2-sub2, 4, 6, 7, 11 and 12). Two actin cDNA clones, ITL-1 and III-12/A1, which have no cloned genomic counterparts, are members of groups IIIA and IIIB, respectively. Homologies at the 3' ends of genes do not extend beyond a short genomic poly(A) sequence, the probable termination of transcription. Homologies at the 5' ends may extend about 300 base-pairs 5' to the ATG but, in most cases, extend only about 150 base-pairs 5' to the ATG. We have identified a group of short, relatively G + C-rich sequences within the extremely A + T-rich sequence at the 5' ends of actin-coding regions, which are shared among different actin genes. Many of these sequences exhibit dyad symmetry, and their general location and order is conserved among the different actin genes. We suggest that they may have a role in regulation of the transcriptional patterns of individual actin genes.
已确定了细胞黏菌盘基网柄菌中17至20个肌动蛋白基因里15个基因的蛋白质编码区两侧的序列。基因间序列比较表明，它们在编码区的5'端和3'端都有广泛的同源性。基于这些同源性，肌动蛋白基因可分为三组。第一组仅由肌动蛋白8组成。第二组由两个紧密相连的基因肌动蛋白3 - sub1和肌动蛋白3 - sub2组成。这两个基因在其TATA框和寡聚（dT）序列的位置上与所有其他肌动蛋白基因不同，并且它们的编码序列也有很大差异。第三组包含我们研究的所有其他基因。在这一组中，有两个基因亚组，IIIA（肌动蛋白5、9和10）和IIIB（肌动蛋白M6、2 - sub1和2 - sub2、4、6、7、11和12）。两个没有克隆基因组对应物的肌动蛋白cDNA克隆ITL - 1和III - 12/A1，分别是IIIA组和IIIB组的成员。基因3'端的同源性不延伸到短的基因组聚腺苷酸序列之外，这可能是转录的终止位置。5'端的同源性可能在ATG上游延伸约300个碱基对，但在大多数情况下，仅在ATG上游延伸约150个碱基对。我们在肌动蛋白编码区5'端极其富含A + T的序列中鉴定出一组短的、相对富含G + C的序列，这些序列在不同的肌动蛋白基因中是共享的。这些序列中的许多表现出二重对称，并且它们的大致位置和顺序在不同的肌动蛋白基因中是保守的。我们认为它们可能在单个肌动蛋白基因转录模式的调控中起作用。
