SPLICING OF THE ALTERNATIVE EXONS OF THE CHICKEN, RAT, AND XENOPUS BETA-TROPOMYOSIN TRANSCRIPTS REQUIRES CLASS-SPECIFIC ELEMENTS

The diversity of protein isoforms is often generated from single genes by alternative splicing of the primary transcript. Using transfection of beta tropomyosin minigene constructs into homologous and heterolog ous cell systems, we show that there are differences, among higher ver tebrates, in the components of the splicing machinery which control th e conserved regulated splicing pattern of two mutually exclusive exons (6A and 6B) present in this gene. These experiments demonstrate that genes which give rise to alternative transcripts may require an approp riate combination of splicing factors which are species-specific, or a t least restricted to the same taxonomic subgroup (class). An importan t practical implication is that the splicing of these genes may be der egulated in heterologous systems in vitro and in vivo, i.e. in transge nic animals.