Nehyba Jirí, Hrdlicková Radmila, Bose Henry R
Section of Molecular Genetics and Microbiology, School of Biological Sciences, and Institute for Cellular and Molecular Biology, University of Texas, Austin, TX, USA.
Mol Biol Evol. 2009 Nov;26(11):2539-50. doi: 10.1093/molbev/msp167. Epub 2009 Jul 28.
This manuscript presents the first extensive phylogenetics analysis of a key family of immune regulators, the interferon regulatory factor (IRF) family. The IRF family encodes transcription factors that play important roles in immune defense, stress responses, reproduction, development, and carcinogenesis. Several times during their evolution, the IRF genes have undergone expansion and diversification. These genes were also completely lost on two separate occasions in large groups of metazoans. The origin of the IRF family coincides with the appearance of multicellularity in animals. IRF genes are present in all principal metazoan groups, including sea sponges, placozoans, comb jellies, cnidarians, and bilaterians. Although the number of IRF family members does not exceed two in sponges and placozoans, this number reached five in cnidarians. At least four additional independent expansions lead up to 11 members in different groups of bilaterians. In contrast, the IRF genes either disappeared or mutated beyond recognition in roundworms and insects, the two groups that include most of the metazoan species. The IRF family separated very early into two branches ultimately leading to vertebrate IRF1 and IRF4 supergroups (SGs). Genes encoding the IRF-SGs are present in all bilaterians and cnidarians. The evolution of vertebrate IRF family members further proceeded with at least two additional steps. First, close to the appearance of the first vertebrate, the IRF family probably expanded to four family members, predecessors of the four vertebrate IRF groups (IRF1, 3, 4, 5 groups). In the second step, 10 vertebrate family members evolved from these four genes, likely as a result of the 2-fold duplication of the entire genome. Interestingly, the IRF family coevolved with the Rel/NF-kappaB family with which it shares some important evolutionary characteristics, including roles in defense responses, metazoan specificity, extensive diversification in vertebrates, and elimination of all family members in nematodes.
本手稿展示了对免疫调节因子关键家族——干扰素调节因子（IRF）家族的首次广泛系统发育分析。IRF家族编码的转录因子在免疫防御、应激反应、繁殖、发育和致癌过程中发挥着重要作用。在其进化过程中，IRF基因多次经历扩增和多样化。这些基因在大型后生动物群体中还曾在两个不同时期完全丢失。IRF家族的起源与动物多细胞性的出现相吻合。IRF基因存在于所有主要的后生动物群体中，包括海绵动物、扁盘动物、栉水母、刺胞动物和两侧对称动物。虽然海绵动物和扁盘动物中的IRF家族成员数量不超过两个，但刺胞动物中的这一数量达到了五个。至少还有四次独立的扩增使得两侧对称动物的不同类群中IRF家族成员多达11个。相比之下，在包括大多数后生动物物种的线虫和昆虫中，IRF基因要么消失，要么发生了无法识别的突变。IRF家族很早就分为两个分支，最终形成了脊椎动物IRF1和IRF4超群（SGs）。编码IRF-SGs的基因存在于所有两侧对称动物和刺胞动物中。脊椎动物IRF家族成员的进化还至少经历了另外两个步骤。首先，在第一批脊椎动物出现时，IRF家族可能扩增为四个家族成员，即四个脊椎动物IRF组（IRF1、3、4、5组）的前身。在第二步中，这四个基因进化出了10个脊椎动物家族成员，这可能是整个基因组两倍复制的结果。有趣的是，IRF家族与Rel/NF-κB家族共同进化，它们具有一些重要的共同进化特征，包括在防御反应中的作用、后生动物特异性、在脊椎动物中的广泛多样化以及在线虫中所有家族成员的消失。
