The cell cycle regulation of structural varients of the mouse histone H4 gene have been analyzed by transfection into L cells with the PSVgpt vector system. Elutriation experiments with the transfected L cells indicate both transcriptional regulation and mRNA stability play a role in the cell cycle dependent expression of the H4 gene. The level of expression and the appropriate regulation of the chicken alpha skeletal and alpha cardiac actin genes in mouse myogenic cells is dependent upon the muscle cell background used for transfection. In contrast the expression of the transfected chicken beta cytoplasmic actin gene decreases during myogenesis in all the muscle cell backgrounds examined to date, in parallel with the endogenous mouse beta action gene. Promoter exchange studies and nuclear runon experiments suggest the decrease in beta actin expression is controlled at the transcriptional level by a region 3' noncoding regions between the chicken alpha cardiac and alpha skeletal actin genes eventhough both genes are expressed in developing muscle. In constrast, the chicken and human alpha cardiac actin genes show 75% homology in these regions. Cytoplasmic myosin gene of acanthamoeba has been isolated. Sequence analysis has defined the transcriptional unit and demonstrated structurally conserved regions shared with other lower and higher eukaryotic myosin genes. PC 12 cells are induced to undergo neuronal differentiation in response to Nerve Growth Factor. A cDNA sequence and the corresponding gene, induced 50-80 fold in 5 hours after NGF treatment, have been isolated and partially characterized. The gene encodes a polypeptide of 85 kD. Gene encoding the muscle specific isoform of pyruvate kinase has been isolated and all the coding exons defined. Expression studies with the mysoin light chain promoters for LC1 and LC3 indicate the promoters do not function out of the context of the entire gene. A gene specific enhancer(s) may control light chain promoter function.
