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The Journal of Experimental Biology 206, 131-139 (2003)
doi: 10.1242/jeb.00067

The myoglobin gene of the Antarctic icefish, Chaenocephalus aceratus, contains a duplicated TATAAAA sequence that interferes with transcription

Deena J. Small^1,2,*, Thomas Moylan^1,, Michael E. Vayda^1,2 and Bruce D. Sidell^1,2,

¹ School of Marine Sciences, University of Maine, Orono, ME 04469, USA
² Department of Biochemistry, Microbiology and Molecular Biology, University of Maine, Orono, ME 04469, USA
^* Present address: Maine Medical Center Research Institute, Center for Molecular Medicine, 81 Research Drive, Scarborough, ME 04074, USA
Present address: Marine Education and Research Center, c/o Biological Sciences Department, California Polytechnic State University, San Luis Obispo, CA 93407, USA

Author for correspondence at address 1 (e-mail: bsidell{at}maine.edu)

Accepted 10 October 2002

Six of the 16 known species of Antarctic icefish (family Channichthyidae) have lost the ability to express cardiac myoglobin (Mb) via at least four independent events during radiation of these species. We report here that the lesion in Chaenocephalus aceratus Mb is a duplicated TATAAAA element that blocks transcription. This lesion is distinct from those of other icefish species that do not express cardiac Mb. The C. aceratus Mb gene is nearly identical to that of Chionodraco rastrospinosus, a closely related Mb-expressing icefish species, with one exception. A 15-bp segment is present in C. aceratus but absent from C. rastrospinosus; this insertion is located 648 bp upstream from the reference transcription start site of C. rastrospinosus and includes the sequence TATAAAA, which bound HeLa cell transcription factor IID (TFIID) and icefish nuclear proteins in gel-retardation assays. Reporter constructs containing the `full-length' C. aceratus Mb promoter were not expressed in transient expression assays in oxidative skeletal muscle of live icefish. By contrast, constructs employing the nearly identical `full-length' C. rastrospinosus Mb promoter were efficiently expressed in parallel assays in the same tissue. Truncated constructs of C. aceratus Mb that did not contain the 15-bp duplication were expressed at very low levels. These data confirm a third independent mechanism of Mb loss among channichthyid species, indicate that C. aceratus aerobic muscle is capable of expressing functional Mb genes and demonstrate that duplication of the muscle-specific TATAAAA sequence in an inappropriate context can result in loss of a gene's expression, resulting in significant physiological consequences.

Key words: myoglobin, Antarctic fish, heart muscle, gene expression, promoter regulation, oxygen transport, icefish, Chaenocephalus aceratus, Channichthyidae

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