Molecular cloning of the human casein kinase II alpha subunit

A human cDNA encoding the alpha subunit of casein kinase II and a partial cDNA encoding the rat homologue were isolated by using a Drosophila casein kinase II cDNA probe. The 2.2-kb human cDNA contains a 1.2-kb open reading frame, 150 nucleotides of 5' leader, and 850 nucleotides of 3' noncoding region. Except for the first 7 deduced amino acids that are missing in the rat cDNA, the 328 amino acids beginning with the amino terminus are identical between human and rat. The Drosophila enzyme sequence is 90% identical with the human casein kinase II sequence, and there is only a single amino acid difference between the published partial bovine sequence and the human sequence. In addition, the C-terminus of the human cDNA has an extra 53 amino acids not present in Drosophila. Northern analysis of rat and human RNA showed predominant bands of 5.5, 3.1, and 1.8 kb. In rat tissues, brain and spleen had the highest levels of casein kinase II alpha subunit specific RNA, while skeletal muscle showed the lowest. Southern analysis of human cultured cell and tissue genomic DNA using the full-length cDNA probe revealed two bands with restriction enzymes that have no recognition sites within the cDNA and three to six bands with enzymes having single internal sites. These results are consistent with the possibility that two genes encode the alpha subunits.     

Mechanism of selection of class II recombinant murine leukemia viruses in the highly leukemic strain CWD

The development of spontaneous lymphomas in CWD mice is associated with the expression of endogenous ecotropic murine leukemia viruses (MuLV) and the formation of recombinant viruses. However, the pattern of substitution of nonecotropic sequences within the envelope genes of the CWD class II recombinant viruses differs from that seen in class I recombinant MuLVs of AKR, C58, and HRS mice. To determine how CWD host genes might influence the envelope gene structure of the recombinant viruses, we characterized the responses of these mice to two different types of exogenous MuLVs. Neonatal mice injected the HRS class I recombinant PTV-1 became infected and developed T-cell lymphomas more rapidly than controls did. The inoculation of CWD mice with the leukemogenic AKR ecotropic virus SL3-3 led to the formation of recombinant MuLVs with a novel genetic structure and class II-like envelope genes, although SL3-3 generates class I recombinants in other strains. These results suggest that the absence of class I recombinant MuLVs in CWD mice is not related to the restriction of the replication or oncogenicity of class I viruses or to the absence of an appropriate ecotropic virus that can generate class I recombinants. More likely, the genes of CWD mice that direct the formation or selection of class II recombinant viruses affect the process of recombination between the ecotropic and nonecotropic envelope gene sequences.     

Action of the cardiac alpha 1-adrenergic receptor. Activation of cyclic AMP degradation

Using purified rat ventricular myocytes and membranes prepared from them, we have previously found that alpha 1-adrenergic stimulation causes decreased cyclic AMP accumulation and decreased activation of cyclic AMP-dependent protein kinase. We have now analyzed the mechanism by which alpha 1 stimulation is linked to cyclic AMP metabolism. In an adenylate cyclase assay in which carbachol inhibits the stimulatory effect of norepinephrine, the addition of prazosin (alpha 1-antagonist) has no effect on the response to norepinephrine. In membranes prepared from myocytes treated with pertussis toxin, norepinephrine competes for alpha 1-receptors (assessed by [3H]prazosin binding) with two components, binding to the high affinity component being sensitive to exogenous GTP, exactly as in membranes prepared from control myocytes. In intact cells labeled with [3H]adenine in which carbachol antagonizes the norepinephrine response, prazosin enhances accumulation of [3H]cyclic AMP due to norepinephrine. Treatment of cells with pertussis toxin eliminates inhibition by carbachol but does not alter prazosin's capacity to enhance the norepinephrine response. Addition of phosphodiesterase inhibitors eliminates this effect of alpha 1 blockade. In [3H]adenine-labeled cells loaded with [3H]cyclic AMP by prior treatment with isoproterenol, alpha 1-adrenergic stimulation enhances disappearance of [3H]cyclic AMP. Measurements of cellular cyclic AMP give results similar to those obtained with the adenine labeling technic. We conclude that occupation of the myocyte alpha 1-receptor results in stimulation of cyclic AMP phosphodiesterase activity.