Different activities of viral enhancer elements before and after stable integration of transfected DNAs.

Analysis of the RNA and DNA levels of a selectable gene linked to a murine retroviral enhancer demonstrated a correlation between RNA levels and tissue-specific enhancer activity during transient expression in T cells but not in stably transformed cell lines.     

Two missense alleles of the Drosophila melanogaster act88F actin gene are strongly antimorphic but only weakly induce synthesis of heat shock proteins.

We have characterized two extant mutations of the flight muscle-specific act88F actin gene of Drosophila melanogaster. Both defective alleles were recovered from flightless mutants isolated previously (K. Mogami and Y. Hotta, Mol. Gen. Genet. 183:409-417, 1981). By directly sequencing the mutant alleles, we demonstrated that in act88FIfm(3)2 a single G-C to A-T transition converted arginine-28 to cysteine and that in act88FIfm(3)4 a single A-T to T-A transversion changed isoleucine-76 to phenylalanine. We showed that the actins encoded by either allele were strongly antimorphic. Mutant alleles effectively disrupted myofibril structure and function in the flight muscles of strains having the diploid complement of wild-type act88F genes. However, unlike antimorphic actins encoded by three previously characterized act88F alleles, neither that encoded by act88FIfm(3)2 nor that encoded by act88FIfm(3)4 was a strong inducer of heat shock protein synthesis.