MOLECULAR ANALYSIS OF BOVINE ACTIN GENE AND PSEUDOGENE SEQUENCES - EXPRESSION OF NONMUSCLE AND STRIATED-MUSCLE ISOFORMS IN ADULT TISSUES

Most studies on the tissue distribution of actin isoform transcripts h ave been done in small mammals such as rat and mouse. We have begun a characterization of the actin gene family in a large mammal, the bovin e. The alpha skeletal gene was isolated, and an isoform-specific probe to the 3' untranslated region of the transcript identified. This prob e, in combination with isoform specific probes for alpha cardiac, beta nonmuscle, and gamma nonmuscle actins, was used to examine expression of nonmuscle and striated muscle actin gene transcription in differen t tissues. In contrast to other species so far examined, striated musc le isoforms were more strictly tissue specific, with virtually no a ca rdiac isoform transcripts detected in skeletal muscle and almost no a skeletal transcripts in cardiac tissue. The distribution of the beta a nd gamma nonmuscle actins was also unique in bovine compared to other species. A partial beta-actin pseudogene, and the chromosomal DNA flan king one end of it, were also cloned and sequenced. This chromosomal s ite was found to be homologous to a viral integration site previously identified in simian virus 40 (SV40)-transformed rat cells, suggesting that this region of the chromosome may be a preferred target for inse rtion events.