Regulation of expression of a Xenopus borealis embryonic/larval alpha 3 skeletal-actin gene.
We have isolated a genomic clone, related in sequence to the skeletal-actin gene sub-family. It is expressed in the skeletal muscle of embryos from the neurula stage onwards and in tadpoles, but not in adults. The equivalent Xenopus laevis gene is expressed as a major transcript in adult muscle, as well as at earlier stages. The intron/exon structure is typical of vertebrate skeletal-actin genes, as is the possession of multiple copies of three serum-response elements in the promoter of this gene. The Xenopus actin and beta-globin genes were fused in their second introns. This construct, which contained 2.4 kb of upstream sequence, was injected into fertilized eggs at the two-cell stage. It showed the normal pattern of tissue-specific transcription. Thus all of the information necessary for appropriate expression of this actin gene in the embryo is contained in the region that extends from a point 2.4 kb upstream of transcription initiation to the centre of the second exon. A series of enhancer constructs were made in which upstream regions of the actin gene were placed upstream of a X. laevis beta-globin gene. The region immediately adjacent to the promoter, containing the three serum-response elements, was able to drive muscle-specific expression, and there was also a general enhancement of transcription by regions further upstream.
Boardman
M
M
Department of Biological Sciences, University of Warwick, Coventry, England.
Cross
G S
GS
Jones
E A
EA
Woodland
H R
HR
D000199:Actins / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004742:Enhancer Elements, Genetic / Q000235:genetics; D005091:Exons; D005786:Gene Expression Regulation; D007438:Introns; D007814:Larva / Q000378:metabolism; D008969:Molecular Sequence Data; D024510:Muscle Development; D009132:Muscles / Q000196:embryology / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid; D014162:Transfection; D014981:Xenopus / Q000196:embryology / Q000235:genetics* / Q000254:growth & development; D014982:Xenopus laevis / Q000235:genetics
D000199:Actins