A novel family of retrotransposon-like elements inXenopus laeviswith a transcript inducible by two growth factors

Abstract

A cDNA clone named 1A11 was isolated in a screen for genes that are activated by both mesoderm inducing factors FGF and activin in animal explants of Xenopus laevis embryos. In undisturbed embryos, 1A11 is expressed during the gastrula stage in the entire marginal zone where mesoderm originates, and later in the somites, the tailbud, and at much lower levels in lateral mesoderm. The 1A11 sequence of 4.5 Kb has a 220 bp repeat at its ends, indicative of a retrotransposon-like structure. A long open reading frame encodes a predicted protein with only short homologies to the gag and protease regions of retroviruses and retrotransposons. Multiple copies of 1A11-related sequences were found in the Xenopus genome, constituting solo LTRs (long terminal repeats) of 1267 bp, and unique region copies (i.e., sequences internal to the repeats in the cDNA). Inverted repeats of 5 bp and apparent target site duplications of 5 bp surround the sequenced solo LTR. Thus, 1A11 is a new retrotransposon-like element in Xenopus laevis.

Characterization of a Xenopus tropicalis Endogenous Retrovirus with Developmental and Stress-Dependent Expression

“…In Xenopus, other TEs are expressed during development and exhibit restricted expression profiles (24,33). However, the expression profiles of TEs during development are different from each other.…”

A novel family of retrotransposons in Xenopus with a developmentally regulated expression

“…To our knowledge, of all retrotransposons only a few LTR-retrotransposons have been reported so far as not containing reverse transcriptase domain in their ORF; 1A11 in Xenopus (Greene et al, 1993), Bs1 in maize (Jin and Bennetzen, 1989), Mammalian apparent LTR-retrotransposon (MaLR) (Smit, 1993), and bik (Vogel and Gerster, 1999). Xretpos contains long terminal repeats (LTRs), primer binding site, and polypurine tract, and its ORF encodes CCHC nucleic acid binding motif of gag gene of retroviruses or retrotransposons.…”

BMP regulates vegetal pole induction centres in early Xenopus development

“…1A). At late neurula stages, muscle actin expression was inhibited and the expression of the 1AA1 ventroposterior marker (Greene et al 1993) was stimulated by BMP-4 injected VPs in Nieuwkoop recombinant explants (Fig. 1B).…”