The skeletal muscle alpha-actin gene of channel catfish (Ictalurus punctatus) and its association with piscine specific SINE elements

The alpha-actin gene of channel catfish (Ictalurus punctatus) was cloned an d sequenced. The gene has a similar organization and exhibited a high level of sequence similarity to those from other vertebrate animals. The upstrea m region of the a-actin gene included a TATA box, a CAAT box, three E-boxes , and a CArG box. Nested deletion segments containing these transcriptional motifs were fused to the reporter gene chloramphenicol acetyl transferase (CAT). Transfection of the clones into C2C12 cells indicated that all these motifs are required for transcriptional activities. The channel catfish a- actin gene is associated with two distinct short interspersed repetitive el ements (SINEs). The first SINE element showed high levels of sequence simil arity to the zebrafish Mermaid element, while the second SINE element is no t similar to the Mermaid element except for an 8 bp sequence CCCCGTGC sugge sting their evolutionary linkage. However, the second SINE element appeared to co-exist with the Mermaid element in most cases and therefore was desig nated as the Merman element. Approximately 9000 copies and 1200 copies of t he Mermaid and Merman elements exist per haploid channel catfish genome, re spectively. BLAST searches indicated that both the Mermaid and the Merman e lements were frequently associated with gene sequences, mostly those of aqu atic animals, suggesting their evolutionary origin in association with aqua tic organisms and their function in shaping the evolution of genomes in aqu atic animals. (C) 2000 Elsevier Science B.V. All rights reserved.