Evolution of the human sarcomeric-actin genes: Evidence for units of selection within the 3′ untranslated regions of the mRNAs

Abstract

The complete 3′ untranslated region (3′UTR) sequence of the human skeletal-actin gene has been compared with the corresponding regions of the rat and chicken skeletal-actin genes. This comparison reveals that the skeletal-actin 3′UTR is composed of conserved and nonconserved segments. By using genomic Southern transfer blots and thermal stability (T_m) measurements, we found that the cardiac-actin gene 3′UTR also consists of conserved and nonconserved segments. Comparison of human andXenopus laevis cardiac-actin mRNA sequences confirms the presence of a region of high similarity in the 3′UTR. We conclude that subsegments of the 3′UTRs of both skeletal- and cardiac-actin genes of birds and mammals are under considerable selective pressure. This suggests that these conserved sequences may have functional roles in actin-gene expression or regulation, and that these roles might be different for each actin isoform.