Department of Veterinary Microbiology and Pathology and School for Global Animal Health, College of Veterinary Medicine, Washington State University, Pullman, WA 99164-6040, USA.
Int J Parasitol. 2012 Feb;42(2):131-8. doi: 10.1016/j.ijpara.2011.10.004. Epub 2011 Nov 22.
Small open reading frame (smorf) genes comprise the second largest Babesia bovis multigene family. All known 44 variant smorf genes are located in close chromosomal proximity to ves1 genes, which encode proteins that mediate cytoadhesion and contribute to immune evasion. In this study, we characterised the general topology of smorf genes and investigated the gene repertoire, transcriptional profile and SMORF expression in two distinct strains, T2Bo and Mo7. Sequence analysis using degenerate primers identified additional smorf genes in each strain and demonstrated that the smorf gene repertoire varies between strains, with conserved and unique genes in both. Smorf genes have multiple semi-conserved and variable blocks, and a large hypervariable insertion in 20 of the 44 genes defines two major branches of the family, termed smorf A and smorf B. A total of 32 smorf genes are simultaneously transcribed in T2Bo strain B. bovis merozoites obtained from deep brain tissue of an acutely infected animal. SMORF peptide-specific antiserum bound in immunoblots to multiple proteins with a range of sizes predicted by smorf genes, confirming translation of smorf gene products from these transcripts. These results indicate that the smorf multigene family is larger than previously described and demonstrate that smorf genes are expressed and are undergoing variation, both within strains and in a lineage-specific pattern independent of strain specificity. The function of these novel proteins is unknown.
小开放阅读框 (smorf) 基因是牛巴贝斯虫第二大亚家族。所有已知的 44 个变异 smorf 基因都位于与 ves1 基因紧密相邻的染色体位置，这些基因编码介导细胞黏附并有助于免疫逃避的蛋白。在这项研究中，我们对 smorf 基因的一般拓扑结构进行了特征描述，并研究了两种不同菌株（T2Bo 和 Mo7）中的基因库、转录谱和 SMORF 表达。使用简并引物进行序列分析，在每种菌株中都鉴定出了额外的 smorf 基因，并表明 smorf 基因库在菌株之间存在差异，在两种菌株中都有保守和独特的基因。smorf 基因具有多个半保守和可变块，在 44 个基因中的 20 个中存在一个大的高变插入，这定义了该家族的两个主要分支，称为 smorf A 和 smorf B。在 T2Bo 菌株的脑深部组织中急性感染动物的裂殖子中，共转录了 32 个 smorf 基因。SMORF 肽特异性抗血清在免疫印迹中与多种大小的蛋白质结合，这些蛋白质的大小由 smorf 基因预测，证实了这些转录物翻译了 smorf 基因产物。这些结果表明，smorf 多基因家族比以前描述的更大，并表明 smorf 基因在菌株内和谱系特异性模式下都在表达并发生变异，而与菌株特异性无关。这些新蛋白的功能未知。
