Halaimia-Toumi N, Casse N, Demattei M V, Renault S, Pradier E, Bigot Y, Laulier M
Laboratoire de Biologie et Génétique Evolutive, E.A. 3565, Université du Maine, Avenue Olivier Messiaen, 72085 Le Mans, France.
J Mol Evol. 2004 Dec;59(6):747-60. doi: 10.1007/s00239-004-2665-0.
Mariner-like elements (MLEs) are classII transposons with highly conserved sequence properties and are widespread in the genome of animal species living in continental environments. We describe here the first full-length MLE found in the genome of a marine crustacean species, the deep-sea hydrothermal crab Bythograea thermydron (Crustacea), named Bytmar1. A comparison of its sequence features with those of the MLEs contained in the genomes of continental species reveals several distinctive characteristics. First, Bytmar1 elements contains an ORF that may encode three transposase isoforms 349, 379, and 398 amino acids (aa) in long. The two biggest proteins are due to the presence of a 30- and 49-aa flag, respectively, at the N-terminal end of the 349-aa cardinal MLE transposase. Their GC contents are also significantly higher than those found in continental MLEs. This feature is mainly due to codon usage in the transposase ORF and directly interferes with the curvature propensities of the Bytmar1 nucleic acid sequence. Such an elevated GC content may interfere with the ability of Bytmar 1 to form an excision complex and, in consequence, with its efficiency to transpose. Finally, the origin of these characteristics and their possible consequences on transposition efficiency are discussed.
水手样元件（MLEs）是具有高度保守序列特性的II类转座子，广泛存在于生活在大陆环境中的动物物种基因组中。我们在此描述了在一种海洋甲壳类动物——深海热液蟹（甲壳纲）热液居蟹（Bythograea thermydron）基因组中发现的首个全长MLE，命名为Bytmar1。将其序列特征与大陆物种基因组中所含的MLEs进行比较，发现了几个独特的特征。首先，Bytmar1元件包含一个开放阅读框（ORF），可能编码三种转座酶同工型，长度分别为349、379和398个氨基酸（aa）。两种较大的蛋白质分别是由于在349个氨基酸的主要MLE转座酶的N末端存在一个30个氨基酸和49个氨基酸的片段。它们的GC含量也显著高于在大陆MLEs中发现的含量。这一特征主要归因于转座酶ORF中的密码子使用情况，并直接影响Bytmar1核酸序列的弯曲倾向。如此高的GC含量可能会干扰Bytmar 1形成切除复合体的能力，进而影响其转座效率。最后，讨论了这些特征的起源及其对转座效率可能产生的影响。
