Calvin B. L. James, Ph.D.

     Viruses, because of their limited number of genes and their total dependence on their host for successful replication, have proven to be excellent models for the study of eucaryotic gene regulation.  Further, it has been documented that transcription of some of the adenovirus early genes and a number of cellular genes, including some oncogenes, is enhanced by phorbol ester tumor promoters.  This discovery has been the basis for the current in vitro model for studying phorbol ester regulation of transcription.  This model uses HeLa whole cell extracts and cloned promoters from phorbol ester responsive and nonresponsive genes to study transcription in an in vitro transcription system.  Recently, the focus has been on efforts to activate the phorbol ester receptor, protein kinase C (PKC), present in whole cell extracts, in an effort to determine its role on transcription of polymerases types II and III transcribed genes of interest.  This system has provided evidence that upon stimulation of PKC, there is a parallel increase in the transcription of adenovirus E1A gene, thus mimicking the in vivo observation.  In contrast, there is inhibition of the adenovirus VA gene and the polymerase III transcription from the P2 promotor of the r-myc oncogene.  These observations allow a direct biochemical test of specificity of the induction of gene expression by phorbol esters, and should lead to an identification of target molecules whose phosphorylation by PKC might play a role in gene regulation.

     Ultimately, this work should provide the basis for a model to define the molecular basis for transmembrane signaling by substances which affect gene regulation.  In addition, the knowledge gained from studies on the regulation of viral and cellular genes could provide the basis for designing substances that could selectively inhibit the regulation of genes.

Selected References:

• Fang Yuan, Karen Auborn and Calvin B. L. James. Altered growth and viral gene expression in human papillomavirus type 16-containing cancer cell lines treated, with progesterone. Cancer Investigation 17, 19-29, 1999.

• Xu, Guang, James, C. B. L.  Protein kinase C inhibits transcription from the  polymerase III promoter of the human  c-Mycgene.  Cancer Letters 123, 199-205, 1998.

• Fry, A. C., Staron, R. S., James, C. B. L., Hikida, R. S., Hagerman, F. C.  Differential titin isoform expression in human skeletal muscle. Acta. Physiol. Scand. 161: 473-479, 1997.

• Qiwei Gai, Guang Xu, T. Shannon and C. James.  Detect ion of specific DNA binding proteins in HeLa whole cell extract.  BioTechniques 22: 1024-1026, 1997.

• Tuck, M. T., James, C. B. L., Kelder, B., and Kopchick, J. Elevation of internal 6-methyladenine mRNA methyltransferase activity after cellular transformation.  Cancer Letters 103, 107-113, 1996.