Combinatorial regulation by promoter and intron 1 regions of the metallothionein SpMTA gene in the sea urchin embryo.
The SpMTA metallothionein gene of the sea urchin Strongylocentrotus purpuratus is regulated developmentally, histospecifically, and by heavy-metal induction. The sequenced 5' flank of the gene can be divided into proximal, middle, and distal regions, each containing a pair of metal response elements (MREs). Canonical 7-bp core sequences are present in all except the middle-region MREs c and d, which contain 1-bp mismatches. Metal-induced expression in transgenic blastulae was increased with each consecutive addition of the middle and distal regions to a chimeric reporter gene construct containing the proximal SpMTA promoter region. Reduced metal induction through point mutation of the distal MREs e and f indicated that the MREs themselves were largely responsible for the transcriptional increase. These activities were further enhanced by SpMTA intron 1, but not when a specific interior region of the intron had been deleted. The atypical MREs c and d did not support induction by themselves, i.e., when present alone with mutated proximal MREs a and b. However, in the presence of intron 1, they were able to substitute for the nullified MREs a and b in the promotion of metal-induced expression. This capability suggests, furthermore, that these atypical MREs, in addition to responding to an intron 1 region, participate cooperatively with the canonical proximal MREs.
Bai
G
G
Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111.
Stuebing
E W
EW
Parker
H R
HR
Harlow
P
P
Nemer
M
M
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002104:Cadmium; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D003001:Cloning, Molecular; D004247:DNA; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation; D007438:Introns; D008156:Luciferases / Q000235:genetics; D008668:Metallothionein / Q000235:genetics*; D008670:Metals; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012617:Sea Urchins / Q000196:embryology; D017384:Sequence Deletion
D008670:Metals; D002104:Cadmium; D004247:DNA; D008668:Metallothionein; D008156:Luciferases; D015500:Chloramphenicol O-Acetyltransferase