α-skeletal actln message levels have been shown to be tightly regulated in chicken primary myoblast cultures. To test for gene elements required for muscle cell specific expression, DNA sequences containing the 5′-flanking regions of the chicken α-skeletal actin, β-cytoplasmic actin, and the histone H2b genes were linked to the coding sequences of the chloramphenicol acetyltransferase gene and transfected into myogenic and non-myogenic cells. In contrast to β-actin CAT hybrids, the α-skeletal actin CAT constructions displayed restricted CAT expression in transfected non-myogenic cells. We showed that a 411 nucleotide fragment flanking the 5′ end of of the α-skeletal actin gene was responsible for a 9-15 fold increase in CAT enzymatic activity during myoblast fusion, versus only a transient 2 fold rise for the β-actin and histone flanking sequences. These results indicate that DNA sequences within 411 bp of the 5′ terminus of the α-skeletal actin gene influenced its cell type and stage specific expression.
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