Evolution of vitellogeain genes: comparative analysis of the nucleotide sequences downstream of the transcription initiation site of fourXenopus laevisand one chicken gene

Abstract

Electron microscopic analysis of heteroduplexes between the most distantly related Xenopus vitellogenin genes (A genes X B genes) has revealed the distribution of homologous regions that have been preferentially conserved after the duplication events that gave rise to the multigene family in Xenopus laevis. DNA sequence analysis was limited to the region downstream of the transcription initiation site of the Xenopus genes A1, B1 and B2 and a comparison with the Xenopus A2 and the major chicken vitellogenin gene is presented. Within the coding regions of the first three exons, nucleotide substitutions resulting in amino acid changes accumulate at a rate similar to that observed in globin genes. This suggests that the duplication event which led to the formation of the A and B ancestral genes in Xenopus laevis occurred about 150 million years ago. Homologous exons of the A1-A2 and B1-B2 gene pairs, which formed about 30 million years ago, show a quite similar sequence divergence. In contrast, A1-A2 homologous introns seem to have evolved much faster than their B1-B2 counterparts.

Mr 25 000 protein, a substrate for protein serine/threonine kinases, is identified as a part of Xenopus laevis vitellogenin B1

“…2); (ii) its nucleic acid sequences closely corresponded to those of both the 5Ј end of the gene and the 3Ј end of the mRNA of Xenopus vitellogenin B1 ( Fig. 3b; Germond et al 1984;Nardelli et al 1987); and (iii) its synthesis in the liver was stimulated by estrogen (Fig. 4d).…”

TheC. elegansvitellogenin genes: short sequence repeats in the promoter regions and homology to the vertebrate genes

“…Figure 3 shows the predicted amino acid sequences of the first 71 residues (encoded by the first three exons) of five vertebrate vitellogenins: one from chick (7,27,28) and four from Xenopus (7,29). Amino acid residues found in at least one vertebrate and one nematode protein are shaded.…”

“…The seven amino acid sequence encoded by the second exon (Fig. 2, between triangles) is the (29) and shows no detectable homology with the corresponding portions of the predicted nematode proteins, although the number of amino acids between regions of homology has been maintained. In the part of the protein encoded by the third exon, the Xenopus Bi sequence is identical to the C. elegans vit-2 sequence at 13 of 51 positions.…”

Activation of chromosomal vitellogenin genes in Xenopus oocytes by pure estrogen receptor and independent activation of albumin genes.

“…In vitro transcription extracts were prepared and UV irradiated in the presence or absence of 6-oxo-estradiol, as described previously (5 Viteliogenin probe. A BglII fragment of the vitellogenin B2 gene running from positions -42 to +220 (8,30) was subcloned into the BamHI site of pSP64. The antisense plasmid was isolated and verified by DNA sequencing.…”